It can be reused for a long time, but after ten or so uses, the color becomes bad enough where you would not want to cook with it.

Yes, it can be re-used several times, but realize that each time you re-use it two important things happen: 1) You build up food particles and silt than can burn, turn black, and generally make everything taste bad like them. Careful filtration between uses can limit this quite a bit, but few people do it. 2) Every time you use the oil you lower its smoke point - the point at which the molecules break down into a funky stuff called acreolein and spread awful smoke around your kitchen in the process. Most common frying oils and vegetable shortenings start out with a smoke point in the 445F range with some lower (olive oil and lard @ 375F) and some higher (safflower @ 510F), so you have some wiggle room. But after you've used it a few times the smoke point starts to drop near your frying temperature, usually around 365F, and smoke begins to rise before you can even get the food in. So if you want to re-use it's probably best to: 1) Fry with safflower oil. The high smoke point it starts with gives you more re-uses before it degrades below your frying temperature. 2) If something you're frying is throwing off a lot of itself into the oil, consider straining it through some cheesecloth between uses. Please wait until it's cool first. Okay, you're right, that was patronizing. I apologize. 3) Don't overload the pan and keep your frying temperature up. Many things fry just fine at around 365F, many people fry lower than that unintentially by stuffing a bunch things into the oil at once. Low frying temperatures let oil into the food and food flavors into the oil. And for heaven's sake have a salad occasionally too.

I've reused a time or two but after it gets a certain color I throw it out. Someone else referenced a lower smoke point after each use. Whoever did, thanks. I didn't realize that before. I mean, I guess it made sense after I had some stuff turn black really quick but at the time I didn't realize that was the reason. I would have mentioned this in a comment but the cell phone I use to do answerbag won't let me comment or ask questions so I have to do it here since I don't get that many opportunities to do answerbag on a computer.

There is a machine called VITO that cleans the oil in your deep fryer making your oil last 50% longer. Call me for more information 507-210-0141 or go to www.systemfiltration.com

It depends on what kind of oil you used. Everything you heat up oil to a high temperature, you lower it's 'flashpoint', the temperature that it can catch on fire. Some oils have a very high flashpoint to start with so you can reuse them if you don't abuse the oil. Peanut oil has the highest flashpoint. It's about 400° the first time you use it but then it goes down about 25° every time you reuse it if you heat it high like 375°. Soy and corn oil are not good longlasting oils. They degrade quite quickly.

There's too many variables to give you a specific time. I will tell you if you keep it in the freezer it (and the food particles in it) will last quite a while yo...