It really depends what you're flying. The 737 is small and cramped compared to the 777 with a bunk. Having flown both long and short haul at the same time you definitely become accustomed to the type of flying you're doing and an 8 or 9 hour flight can fly by quickly. When you go from that to SH a 1 or 2 hour sector seems instantaneous. Return to LH and an 8 hour sector feels like forever, but after a couple you get used to it again.