The life of 99% of generators is the same, nap till needed, and you better be ready and able when needed. The napping place is generally the worst possible location, generally damp and dank. Generators don't nap happily, they loose their residual magnetism and the capacitors that excite them go bad. If it's a 3600rpm machine multiply failure factors by 9.
Happy generators start once a month, and run with at least 50% load for half an hour so they can warm their windings and cook off any condensation. They have oil that isn't loaded with condensation, and they are excited and ready to go when the PoCo craps out. Their owners don't call Phil to tell me the power went out, they found their generator, it runs and no electrons are coming out. They don't have owners who hear Phil say he will give them a call when he gets back from Phoenix or whatever far away place comes to Phil's mind that moment.
