I agree with both of gbopp's post. I think that a generator performs better if it is exercised on a regular basis. We even exercised our standby and main generators in the utility industry.
I believe that the generator should stabilize before load is put on it, just like an auto transfer switch would do. Since you have a plug I would turn off or open the main breaker then plug in. After plugging in I would turn on or close the main breaker. Circuit breakers are made to take the arc that is created when current passes through the contacts, prongs on the plug are not made for that. I have also seen plugs explode when removed with high current on them. It is uncommon , but it does happen. JMO
