You are only allowed to park at truck stops while sleeping and utilizing the truck stop. In other words it is for paying customers. Many businesses in town will have a trucker towed if they use their parking lots and so no there is not really anywhere for him to park.

Is it the rig and trailer or just the rig? If it is the rig then stop being a pain in the butt, a truckers life is hard enough and so is the girlfriend's life being with a trucker. I was once married to a trucker and they are home maybe 2 to 4 days every 2 or 3 weeks. If it is a nightly thing then he should have a local company that he can park the truck in their trucking yard. But seriously if you are complaining about a total of 5-6 days out of the month just stop being petty and let them be.