The problem, as Long Haul sees it, is that he gets all the work and very little of the excitement and the glory that goes with being a Decepticon. He knows his job is important; he'd just much rather be on the front lines fighting shoulder to shoulder with fellow warriors than moving supplies and building installations to make sure those warriors continue fighting. Long Haul keeps these secret desires to himself though, as he's smart enough to know Megatron is not likely to be sympathetic and has no patience for grunts who question their orders.
He also serves as Devastator's crotch. Tough break.
Some time in the past, Long Haul and the other Constructicons were responsible for creating Megatron. Five Faces of Darkness, Part 4 Roughly nine million years ago, Long Haul and the Constructicons were friends of Omega Supreme in Crystal City on Cybertron. Their engineering skills were permanently turned to evil, however, once Megatron and the Robo-Smasher reprogrammed them into Decepticons. They were also given the combined form of Devastator, making them the physical equal of Omega Supreme in combat. After they destroyed Crystal City at Megatron's command, the Constructicons earned the everlasting ire of their former friend.