It is very common for generators to have shortened lives because of either low engine loading or just lack of use at all.
Assuming mechanical, I would estimate 35% being a safe minimum and you'd probably want to run it once a week for several hours. Certainly higher loading is better, but unless you're running your aircon, it may be difficult to provide such a high load. Perhaps timing water heater, battery bank bulk charge, electric oven and clothes washer/dryer.
I guess I neglected to mention that our last genset was a running take out at 19,000 hours plus. Certainly not without some problems at the end like rusting out freeze plugs and the alloy water pump housing corroding, but none the less a running take out.
As for operating our genset, it gets at least an hour in the morning and evening 365, with a water heater, high amp battery charger, fridge/freezer, and various kitchen appliances during cooking. When not cooking, the 35 gph watermaker goes on with its 17 amp draw, so I'm guessing a light load or little use won't be the death of this one.
In the marine field, I believe electronics are a big mistake in both gensets and main engines. Spare pc boards deteriorate at nearly the same rate as those in use and they are expensive
. A good old mechanically regulated genset and main engine are worth their weight in gold if one is beyond the reach of Sea Tow or speedy delivery (1 day overnight usually takes about a week here).