Oils deterioriate with heating and with the frying of certain foods. Oils used at a lower heat or for frying lower protein foods will last longer. Oils used at higher heats or with higher protein foods will deteriorate faster.
Also, oils deterioriate when reused. Withe each reheating, the smoke point of the oil drops and foods will brown prematurely before they are cooked through.
Neutral flavored stable oils with high smoke points are best. Peanut oil is the standard for home use.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan