Yes cooking oil can be reused after deep frying foods.
You can safely cook with the same cooking oil in the deep fryer for around 15 to 20 times and sometimes longer.
But the more you cook or deep fry the foods in the same cooking oil the cooking oil begins to break down and then turn to a black color or at least a darker color.
So after around 15 to 20 times it's best to change the cooking oil in the deep fryer.
I only change my deep fryers cooking oil when needed and reuse my cooking oil in the deep fryer several times before changing it out.