We are the SMD, an association of Christian student unions in Germany. Although we do have some supporting full-time staff members, all of the work in our local chapters and quite a bit of the work in our national leadership is the responsibility of student volunteers (like myself).
Speaking locally: if we as students want something to happen, we make it happen - if we don't, it doesn't. Obviously, attendance at our events varies widely between term-time and holiday-time, but we do have enough active members to guarantee our weekly meetings taking place whenever.
Of course, recruiting new active members is a constant and central challenge, but thankfully, my group has been able to maintain a pretty good level (~20 active members out of ~60 regular visitors). Most of the work our regional full-time staff do relates to coaching these active members, and especially the group leaders they elect each semester.
Does that answer your questions, or did you want to know something else too?