I played a six hour New Years Eve gig once. The restaurant ended up short that evening and we went home with only half our pay. Yuck!
I've recently been to a gig where the band (some friends) played what I consider a very long six hours at a bar. They weren't paid well either. Oddly, they had plenty of musicians to play the show and took turns featuring different vocalists including a few songs with me. The place was nothing special, just your below average dive. The audience, other than the musicians and their mates, was just another drunkathon crowd that could care less about what was happening on stage. Even the music was reduced to what was easiest for all the various participants to follow, typical electric blues/rock styled bar band stuff.
No, I don't think that this is the norm for gigs here in the states but I'm certain there are exceptions, as there are to any rule. Most of the shows that I've played have been between one to three 45 minute sets. It depends upon the venue and what they require.