deb, here's a link to a previous discussion on this:
Deep Fry Oil Reuse
there a chinese take out by my job that makes awesome thrice fried chicken. that is they fry it most of the way done at 11am when they open. then they fry any 1/2 chickens that haven't been sold again at around 3pm to keep it warm and kill any growing bacteria, when the local kids get out of school. then, it is fried a third time, hence thrice fried, when you order it to go.
it's actually good at noon, after only 1 frying, in fresh oil. but by 5pm, much of the oil is adulterated with chicken fat after having fried dozens of birdies, as well as the chicken sitting there partially fried all day. yuk!