Mileage can certainly be used without having to be associated with literal miles.
Freedictionary defines it as an informal noun, meaning usefulness, or how much service something has provided, or may provide.
Cambridge dictionaries defines it as an advantage that can be obtained from a situation
A person may get good mileage out of a situation, meaning that they made good use of, or made good benefit from a situation. My very old clothes dryer is over 15 years old, and although it now needs replacing, I would say I got excellent mileage from it.