I honestly don’t know. I cook all the time, but never deep-fry anything. It seems like so much oil is wasted, and such a mess to clean up. So how does that work?
When I worked in a restaurant we didn’t change the oil everyday since, as you say, it would be a great waste and it can be reused.
At home, you’re supposed to put it into a disposable container and throw it out with your trash. cite
I was having a conversation about this with a Japanese friend today and she mentioned that they sell something here which, if added to cooking oil, makes it solidify so that it can be thrown out without using a container. I have no idea if it’s available in the US.
Many juicy vegetables will add too much water and many meats will change the flavor of the oil. These necessitate more frequent changes of oil, but it generally can be used more than once. As it can be a bit wasteful it is best to have a fry party and cook a bunch of stuff in one evening (keep the Alka Seltzer handy). I pour the used oil on the compost pile.
If you filter your oil when you’re done cooking (after it’s cooled, obviously) and keep it covered and out of the light, you can have it last for a while. Certain fats last longer than others, but it seems to work conversely with the ones that are best for frying. Peanut oil is one of the best, but because it’s mostly unsaturated, it goes rancid easier. Safflower and canola oil are good “middle of the road” ones that have a decent mix of high smoke point, neutral flavor, and decent shelf life.
You know it’s time to change the oil when it smells like it’s time to change the oil. 
You can turn it into biodiesel!
We tend to reuse it. We don’t deep fry very often, but about once a year, we buy a new gallon of oil, and after each use filter it, and return it to the original container. We mark each use on the bottle with a sharpie. It’s stored in our cool, dark pantry closet.
If it begins to smell bad, or discolor badly, we discard, and get a new one. We generally get 5-10 uses (we’re not using the whole gallon at a time), before we feel we need to throw it out.
Our disposal generally comes during one of our annual brush burns. Cooking oil burns nicely on a bonfire! 
If no bonfire is forthcoming, it gets dumped in the woods behind the house.
CCKERBEROS, a post in another thread mentioned the difficulty of oil disposal in Japan. What are the difficulties? Is it the container use as you mention in post #2?
Empty milk cartons work very well for disposal. Make sure it’s cooled, of course.
I’m an ambitious but lazy cook. When I deep fry, I usually eat a few deep fried meals in a row and just keep using the oil until it is gnarly. When I have a pot of deep fry oil going, I’ll even sneak bits of it off to in my day to day cooking, which surely isn’t ideal, but gets me fed. Usually my pot of oil is reasonably depleted by the time it goes off.
If you’ve never tried it, it is worth trying. Deep frying is really easy and the results always seem really special. My favorites are samosas and homemade potato chips. But don’t be tempted to skimp on the oil. Deep fried food needs to move while it cooks, and if you don’t have a nice deep pot of oil you’ll get frustrated with small batches and hard to control temperatures.
This might be considered a bad idea, but I’ve never experienced any ill effects from it in 6+ years. I pour a LOT of dish detergent into the oil, and then spray it with hot water until I get a saturated, sudsy/soapy emulsion. I pour this down the kitchen sink with the hot water running and leave it running for a couple of minutes.
I don’t deep fry very often so I do this about once every 2-3 months. My drain has never clogged.
I thought it was a bad idea to compost oils or oily foods, because it would attract rodents.
I don’t reuse it, but I don’t fry very often. I let it cool, then pour it into an empty 2 or 3 liter coke bottle, close the cap, then put it in the garbage can.
I have no idea what seodoa is referring to. A quick net search turned up a Nisshin page (Japanese) explaining how to dispose of used cooking oil. It lists the two methods I mentioned in my post above, as well as a third (soaking up the oil in newspapers and then throwing it out.) The Osaka municipal homepage (also Japanese) agrees.
Our area garbage collection wants no liquid in the garbage. dried out old paint is fine, just open the lid and let it sit. They say on the pamphlet that cooking oil is biodegradable and to prevent attracting scavengers, simply dig up a spot in the corner of your yard or garden, dump the used oil in and bury it. If you are out in the woods, dumping it on the ground far from the house you should be fine.
I don’t deep fry stuff very often but if I have waste grease or oil, I add it to my dog’s food, a tablespoon or two at a time.
I used to work at a fast food restaurant that was very busy. Once a week, on Sundays, we would clean out the deep fryers by removing all of the oil in there and storing it in large barrels. After a week of usage, the oil would be less clear and transparent from all of the fries and chicken we would use it for. It was a safety concern with us, but I’m not sure if anyone’s ever gotten sick from it as we would dump new oil into it during the week when it was getting low.
The barrels were collected every week by a recycling company. Apparently that episode on the Simpsons with Homer being a grease baron was real. I dont know what they do with it actually, but old oil is actually worth something to people
Darling International is one of the companies in this business. They are also in the rendering business, using inedible byproducts from food processing operations. Their site will have some blurbs on what they do with it:
It can be lucrative. Apparently, one of the problems for a company like DAR is trying to standardize operations for something which has typically been handled by local contractors.
Don’t add fats to your compost; it slows the composting process.
This stuff burns, right?
The threat of being overwhelmed by rodents from the addition of a gallon of oil every other month is probably overexaggerated. Furthermore, I have no issue with slow composting.
Indeed. There’s lots of rubbish talked about composting (heh) - don’t put this or that on the pile. As long as you have a reasonably well constructed compost bin you can throw most kitchen waste on there without a problem. The only things I avoid are large bones, as they don’t break down. Corn cobs take ages to decompose, too, unless you chop them up.