Assume that you get up at the usual time in the morning, and don’t leave until nighttime. Feel free to account for differences if you’re domestic or international, and how long your return flight is.
Oops, assumption is already upside-down to what I do. The last day of vacation is the day I travel; if possible, by car, but in any case and being a morning person, I much prefer to arrive home while I’m still feeling alive. If I have no choice but to arrive at oh-god-o’clock, then the last day of vacation is the day I’m already home: there shall be laundry. And vegging. And possibly deli food. I’m a fan of whomever came up with the idea of takeout, it makes landing back home so much easier.
I treat it as a travel and recovery day. We’ll make a small stop or two along the way (that is how we found Uranus) but mostly its that day to set ourselves up for the return to the real world.
Ideally, I schedule my return for late morning. If I don’t leave until nighttime, this is an extra day at my destination.
We prefer to leave a free day at home following a vacation for the decompression time.
I try and time my return to be on a Saturday, with Sunday to get my life back to normal before work.
Saturday is a travel day, generally involving an airport, so there isn’t much holiday time about it.
The last day is usually mostly travel. Sometimes i can squeeze something else in, but not usually.
I never count the buffer day (e.g., Sunday) as part of the vacation. That day is a buffer (in case of delays), but mostly for decompression, laundry, and cleaning.
Given the specs in the OP, though, if I have a late flight, I’ll fill the time during the day with whatever I can, allowing for anywhere from one to three hours for getting through the airport to my flight. In general, though, early flights have a lot less likelihood of being delayed or cancelled, so I avoid them when economics allows it.
We do the same routine every year after a week or two in St Martin. Rise with the sun, eat whatever breakfast stuff is left in the fridge; brioche, cheese, mango, bananas. Do a breakfast shot or two chased with a Carib. Any leftover liquor/beer gets taken down to the bar and donated to whoever is drinking in the morning.
Then we pack. Checkout time is 10 or 11 (we never know for sure and have to check). Take a shower then apply sunscreen. Load bags in rental car. Checkout. Go to airport and leave checked bags.
Go to Rusty Rocket (dive bar near airport) and drown our sorrows. Get a little shitfaced. At last possible moment drive back to airport, return car, and deal with boarding. The flight home sucks, since there are no direct flights and we have to go through customs/immigration at the first US airport connection.
Arrive home at 2 am. Deal with transitioning from 80 degrees to minus 5. Get disapproving looks from gf for wearing shorts and a Hawaiian shirt. 
We usually try to get an afternoon flight back home, and the half-day before the flight gives us time to do anything we’ve missed out on. Sometimes that’s just walking around, buying souvenirs, and having a snack or lunch. Other times, we’ll go to a sight or museum we skipped because it was too busy, or we saw it on the way to doing something else.
Also, laundry=chores. Those are for after the vacation.
Recently returned to the US from Japan. After gallivanting around the country, we stayed in Nagoya the night before our flight home. On the day of departure we had a nice breakfast, then packed our suitcases and duffle bags (this takes a while; we buy a lot of stuff during these trips, and it’s a challenge to get the weight distributed and ensure that delicate items are adequately protected. After that, we went shopping for some tasty food to take with us for a lunch at the airport (Japanese department store basements typically feature a massive selection of really good ready-to-eat foods that are packed to go). Headed to the airport around 1PM (30’ train ride), ate our lunch at the food court tables outside of the secure area, and then my wife browsed the shops while I watched planes come and go (NGO has a nice outdoor observation deck on top of the concourse, very popular with planespotters). Flight home departed about 4:30.
I’m always concerned about encountering a delay that could make us miss our flight. There’s only one flight home per day, and changing it would be extremely expensive and inconvenient (change fee, fare difference, extra hotel night, schlepping all of our stuff back downtown and then back to the airport the next day). This is why we stay in Nagoya the night before flying home, and it’s why we show up at the airport about three hours before departure. A few years ago I flew home next to a guy who was on my plane because he had missed his flight home the day before: he had been on the train to the airport when someone jumped in front of it. Not sure if our margins would have let us get to our flight under the same circumstances, but I’d put good odds on it.
Until recently we would fly back from the west on a redeye, so we’d typically pack up, load the car, drive several hours to our airport town, stopping along the way for a little easy sightseeing or a meal, get to the airport, return our rental car, dinner in the airport and fly home on Saturday night, arriving home Sunday morning.
Lately we’ve been spending Saturday night in the airport town (typically Vegas) and enjoying the day. This year it was a hike on the way to Vegas, relaxing afternoon, catching a show, late dinner, then fly home in the morning.
Coming home from Europe it’s mostly been pack up in the morning, get to the airport, and fly home.
I only go to events - races, festivals, etc. where I am somehow a part of it other than “spectator”. For races I am either a participant or on the staff producing the race.
Three times already this year I’ve done ‘away’ races. Twice was get up early, check out of hotel, go to race, complete race, drive hours home while the third one was get up early, do (ultra-distance) race, go back to hotel, shower, pack, head to airport for flight(s) home.
We always go to a festival Memorial Day weekend. This year was get up extra early - 4:30 (for a photo op) instead of the usual 5:10. Get photos, jump on chase, stop for some more photo ops on the way back, pack up, clean up (we have a group rent a conference center - we bring all food to cook & snacks with us). Then it was detour an hour out of the way on an otherwise 5 hr drive home to go to a second Grand Canyon, some hiking & photos before finally getting home after 8pm. Unpacking probably took another ½ hour.
Yeah, the CIA would get more out of me making me lie on a beach than if they waterboarded me.
Last day is usually a travel day because we do a lot of international trips, but I have been on a couple of beach vacations where I am on the beach in the morning and travel in the afternoon. No reason to end your vacation while you are still on it.
If we are at one of my SIL’s Worldmark retreats, the car was packed the night before, so I get up first at go soak in the hot tub and wait until the others are up, then we go out for breakfast at a local spot, then drive home.
It depends. From Europe, I’ve never seen a flight to the USA that leaves later than early afternoon and three hours check in at the airport is recommended. So, if I do anything, it will be just grabbing some cheap last minute souvenirs for everyone that wanted something.
Domestically, it also depends. From Washington DC, it’s only one time zone and a short flight, so I take a late flight home and have almost another day. There’s a flight that leaves at 7, so if I’m on the metro by 4, I get to DCA around 5 and I’m good. That’s the second to last flight of the day, so I have a bit of a cushion.
My wife and I go to Barbados for three weeks every winter. The flight back leaves around 3 and takes five hours, but we gain an hour so land around 7. We get home usually a bit after 8, have a light supper and go to bed early.
We try to get to the airport not much after noon; Air Canada usually has long lines since the flights to both Montreal and Toronto are full and leave rather close to each other. In past years we have tried to get a dip in the ocean the last morning, but have given up on that. So we pack, laze around finishing up our food and wait for the taxi before noon. When I get to the airport, I check the luggage in and then go to the local fast food emporium and get a couple of stuffed roti to eat on the plane and then we go through all the rest of the airport theater and then sit and wait a while.
I go to Thailand every February. The last day I pack. I also buy souvenirs which end up costing more than I can take out on my ATM card. So I have to call my bank to increase my limit. Then I sit in the bar at my hotel drinking beer until it’s time to leave for the airport. I hate the last day