My DD does L4 and goes about (3 days) 10 hrs week. Our L5's go more, 3 nights a week & Sat for about 15 hrs. I suppose every gym has different schedules depending on how competative they are. Our L5's are new, just moved up from L4 (we did not have a L5 team before that for a few years) so they are working on learning the routines to be able to compete ASAP.
Sounds like you've been bit by the gymnastics bug, LOL. My DD loves being in the gym & might complain if she were only there 6 hours. Maybe you will get the additional hours when you move up?