I leave mine leveled when its parked for storage just so the doors and such operate good. I can leave my wood blocks in place at home, so I just back in the same spot every time, its already leveled when I unhitch and lower the front down.
I have around 30 years of experience using the gas RV Norcold and Dometic fridges, never had a single issue running them mildly out of level. I do avoid keeping them way out of level though. The residential fridges run better when they are close to level too they say, but we never had an issue with our big double door residential set up either. Ice cream didn't melt. My home fridge isn't as level as my RV fridge.... old flimsy house...