[fargus111111111]

As was already mentioned scheduling depends alot on what the schedule of mentors and members looks like however one thing that has always worked for my team is that we have someone at the shop every night during build season and others come what ever nights they can make it. This enables many members to work around their jobs and school activities.
Years that we are large enough that our budget cannot support every one going on the trip we do lay out hours and behavioral requirements to go on the trip. Usually anyone who still shows regularly at the end of the school year gets a letter.
I think a large part of our members not getting burt out is getting something to start testing fast because then we can play with it and our method of meeting, come when it is most convenient for you.