I don't deep fry often, but when I fry it's days of frying because of the hassle of preparation and dealing with the lard I use for oil. Our house layout allows me to have the deep fryer just outside the kitchen on the deck because I also avoid the heavy smell of frying oil in the house.
I have a batch of oil that only sees french fries and other things that don't include fish i.e. twice fried Korean chicken. The other batch gets used for anything resembling fish: deep fried fish fillets, prawn tempura, salt and pepper squid, and my wife's favorite, calamari.
I've learned to pay close attention and remove stray bits of food from the oil before they burn and not to get the oil too hot. Then strain when done into containers made for that purpose (found on Amazon)and then into the deep freeze until the next time. Minimize those chemical processes going on in the oil...
When a taste test of the oil says it's done, it's done, no matter how many times it has been used. Where we live, Chefstore sells pails of lard for frying cheap like borsch.