I agree the generator system should be exercised at least once a month. The single point of failure there would be the transfer relay and knowing the status of that would be crucial for me before finding myself stranded up the road somewhere.
I think you will find most folks on here running theirs for 30 minutes to an hour on a scheduled basis...
We Ham Radio guys that have backup generators usually run our operations every Saturday running off the generator just to make sure all is still in running good...
My 2KW Honda Generator sits secured in the tailgate corner of my covered and locked truck bed and goes where I go. It is surprising how often it gets operated for one thing or another. Certain does not just sit there.
Roy Ken