Most of our gigs are 3 hours, the minority are 4 and the longest gigs we've done are 6 hours.
I'm not surprised as I believe for the gigs you do are "we are the entertainment". Hopefully you get at least a couple of short breaks in the 3 or 4 hours. As a DJ I could plan my own toilet breaks with a 12" single or something (which was just as well).
Some of the long gigs I did had a break for a meal, so I could just stick on some good music and relax for the duration. Often I'd get fed, too, which was nice. Especially so when they had a proper sit-down and went to the trouble to organise a vegetarian meal for me. Now that's really nice! Long gig I took sandwiches to be sure.
I loved doing it and sometimes miss it, but I found my tastes in music were advancing far faster than my audiences' were. I found myself starting to 'accidentally' leave behind songs I couldn't any longer bear to play, and longing to play the really good, newer, more exciting fusion stuff that was still rising. I faced a three-way choice. Focus on the weddings and the like, where music tend to be MoR; go for broke in the high-end clubs; or quit whilst I was still having fun. I chose the latter. With hindsight I think I'm glad I did, because music started to regress (IMHO) into the drum-n-base and similar genres. -- That's not for me.
Enough ... I'm off-topic.