never if you have a good running unit. most charges last 10+ years if no issues with sealed system. you can't just fill it up if you don't know how, don't have equipment and certification for use of. as long as all other parts are operating correctly- freezer warms up, along with fridge; depending on model the evaporator coils (in freezer) will frost only at top areas and not the rest, indicating sealed system restriction or low freon. depending on age might be warranty issue and also, the freon doesnt just disappear, it most likely would have a leak and putting more freon won't fix leak.
