I have one on my key chain, along with the remote. I keep a second one in my wallet. While the key or remote is needed to lock the car, after it is locked it would be possible to lose the key chain and be locked out.
Years ago when I lived in Washington DC I also locked my keys in the car with the motor running while shopping. I had to go across town to my apartment to get the spare key. Since then, I’ve always tried to have a backup somewhere.
I always carry a spare in my purse. I have locked myself out of the car a half dozen times or so. And my SO also carries a copy, and I have a copy of his too.
I have two, on two different rings. Only once have I locked one in the car, and it was 20 years ago, and at the time, I only had one key. In a major coincidence, the business that I had parked in front of was having lock problems, and a locksmith was on the way already!
It also makes it easy to leave the car running - I can lock the door, so no worry about someone running off with my car.
Joe
Ah…I’m starting to see a definite correlation between “I like to keep the motor running” and “I have two car keys”.
It’s probably been 15-20 years since I locked my car with the key inside. And before then, low technology was my friend. For instance, the VW Super Beetle I had from 1975-82 was easy to break into with a coat hanger. And from 1987-96, I had a small pickup with a camper top, and the camper top had side windows that could be wiggled open over the course of 10 minutes’ effort. So I kept a toolbox under one of the windows, and I kept a spare key in the toolbox.
My car is programmed in lock-out prevention mode, so if the keys are still in the ignition and the car is off, the doors won’t lock. You can lock them in the car with the engine running though.
The car also came with a handy little half key for the door in a little plastic case the size of a credit card that I keep in my wallet and is enough to open the door.
No extended warranty for me, thanks. Their cost generally exceeds their expected value, which is to say they’re a bad deal for the buyer. Actually the same is true of just about any insurance policy, but buying insurance in some cases makes sense in some cases (home, heath, auto, and life) because the cost of losing (e.g. if your house burns down) can be financially ruinous.
FTR I’m not risk-averse, but I do try hard to manage/mitigate risk where the cost for doing so is small. Example: I’ll happily ride a sport-touring motorcycle half way across the country, and then and carve up the canyons when I get there - but I wear a full face helmet and armored jacket/pants/gloves/boots in case I have a get-off, and I pack a number of cheap, small easy-to-carry spare parts (and tools) with me in case the bike breaks down. Oh yeah, and a spare key, too. 
As described earlier, I already have two separate keyrings anyway, so we’re talking about adding one more key to one of the rings. IMHO the cost/disbenefit of carrying a second key with me is minimal and confers substantial benefits.
OTOH , this - sitting on your hands every work day for 45 minutes (as opposed to just once. for twenty minutes.) is costly and confers minimal benefit.
One, unless I’m traveling over 100 miles from home. If I’m closer, it is easy for my SO or a friend to drop by and pick the spare up and bring it to me; farther from home it would be an expensive hassle. And it’s not that I’m afraid of locking the key inside the car - keys are really hard to lock in the car these days, since most use the fob to lock the door - I’m more afraid of losing the key other places. 1000 miles away from home and I lose my car key = a more expensive road trip by about $350 (more if it takes a few days to replace from the dealer).
One, but I developed the habit of keeping my car keys in my hand until I get out and shut the door. That means no putting them in my jacket pocket, then throwing the jacket back in the car because I decide it’s nice enough to not need a jacket, then shutting the door. It’s also much harder to lock the keys in now that I have a fob for locking the doors.
When we travel, we usually take our car, and both Jim and I have a set of car keys on us at all times. We’d have to do something special to lock both sets of keys in the car.
One. My car has a keypad on the driver’s door.
Buying an extra key, which takes 10 minutes of my time at most, is the same as 45 minutes of waiting in a parking lot? Makes no sense to me. I have had a flat twice in my life. I have locked my keys in the car half a dozen times, as I said. I hate the feeling so much so I started carrying an extra key at all times. I do not buy extended warranties, however, I do research all of my stuff thoroughly that I buy. As for a car loan, I only buy used cars and pay them off as quick as I can.
I mean, those things aren’t remotely analogous to keeping an extra car key.
Cat Whisperer I also keep my keys in my hand. Yes, I am anal about my keys because I have lost them before. i go home and they always go to the same place and I always keep aware of them wherever I am. I want to be able to reach for them and instantly find them.
Less than 10 bucks I think. I’ve never had a vehicle with a “chipped” key so I dunno about that.
I have a husband and five kids who live in this town. One of them would be able to bring me an extra key if I was to lock my keys up near home. If we go out of town hubby and I each have a key ring.
I only carry one key. I also keep one key in my car for other purposes, like lending out the vehicle or so I’d have an option if I lost the key I carry.
If I locked my main key in the car it would be an inconvenience. I’m confident in my ability to not lock my keys in the car. I’m pretty proficient in breaking into cars when I have tools available. I’m willing to pay a locksmith to come out if need be. If all else fails I can break a window and use the key I keep in the car.
My husband and I are both that way, with all of our daily travel stuff (purse, wallet, keys, sunglasses, cellphones, etc.). They go in the same place every day, and we always know where they are. It seems such an obvious, easy solution to me that I don’t understand people who are always searching for stuff.
The poll missed my option of: One: I’ve locked my keys inside my car once and that was enough to teach me a lesson.
Of course I manged to lock my keys in the car with my 3 day old infant on a frigid day in March so it was a particularly intense lesson.
I began doing this when I locked my keys in my truck 400 miles from home. I got to the local GM dealership 10 minutes before closing after calling in the VIN. They had a key waiting for me (fortunately, they knew my family, so they knew that I wasn’t a random car thief 
). It cost all of $10.
I changed this to carrying a spare in my pocket when I travel and one at my BFF’s house when I’m close to home after my billfold was stolen about six weeks ago. I immediately realized that not only did the thief have my money, all of my cards and my address, but s/he also had the key to my vehicle. :smack:
We must be the only ones with keypads to unlock the doors. I thought those were a bit more common.
It is hard to lock the keys in my car. I would have to go out of my way (do things differently than I normally do) and want to do it.
One on me and one in the glove compartment. If you’re going to steal the car, you’re going to steal it. I carry the second one on my person if I"m travelling out of town. I tend to lose things more often when I’m not in my usual surroundings.
I store my car key in the ignition of said car. I don’t own keys to my house. It’s been this way since 1991. 