Is there a tool for preventing the generator from running too often?

You can use the minimum load ratio to avoid running the generator at too low of a load.  It's not good to run diesel generators, for example, below some about 25% (or maybe 50% depending on the model) of their fullyrated capacity, or else condensation can occur in the exhaust system.

That causes corrosion and a shortening of lifetime or at least increased maintenance cost.

The minimum load ratio has no direct effect on the operating hours of the generator. It is simply a constraint on how low the generator power output can go.  Raising the minimum load ratio, however, could indirectly lead to fewer operating hours because the generator is more productive when it runs.