When we are on the road, we make a point of running the generator for both breaks and lunch. 5-10 or so minutes before approaching a rest stop we'll run the generator and kick in the AC. If it's winter we'll run the heat pump. If you do this frequently while you are on the road, this will help keep your generator in good working condition. Leaving the rest stop, allow the generator to continue running for a few more minutes so as to give it a good 20 to 30 minute run.
If you need to run the generator while parked, disconnect the shore power and run it under a load. I know people that buy brand new motorhomes, drive them to Florida, do work kamping, sit tight for 7 to 8 months and don't run or move anything.
Too many lawn clackers, screen rooms etc. in the way I guess.
When we were running out in the South West in the summer (July - August) we ran the generator & coach air all the time along with the dash air. Even then, it was never cool in the rig - just tolerable.