can i ask do the gms have like a year or something that they are gms and once its over they are out or what?

nope

once you sign up your in it for lyfe

unless ofc u quit or really inactive

as Kirito said, once you get accepted, you are there as long as you are active and do your stuff.

Keep in mind we do have lives as well, and sometimes that takes priority, and people step down from their position to focus on school or whatever.

Ok I get it now say if someone steps down because he/she quit and then if he/she comes back do thy need to apply again for gm

Yes, however in some cases they skip the trial phase or its shortened greatly.

Thank you and closing