First withdrawl? Been there… twice now!! Im not sure if the original post was intended to mean over the summer, or when you leave a team… ie college…
Heres how I delt:
Graduated HS 1998, couldnt leave FIRST, originally wanted to go to a college that had it, so I applied to a bunch… however I found that Clarkson would be willing to give me money to start a brand new FIRST team (thus FIRST withdrawl avoided!) I spent the entire summer planning for the new team.
College 00-02, had a hard time balancing an engineering degree, varsity skiing, and FIRST, so while I cut back on the team, I ended up volunteering at the competitions (including nats!) what fun!!
Same when I left college, 03 I couldnt stay away, so I volunteered again (not to mention kept tabs on my HS and college teams!)
Finally started to get the itch to dive back in early this year, mentioned it to the Clarkson team (perhaps mistakenly!!! :ahh: ) and ended up getting my name passed to parents in Penfield… thus getting sucked right back in! I’ve been planning this team since February '02 this year, and now its here! yeah, no more withdrawl!
So I guess my advice is, if you mean you are having withdrawl from FIRST itself(ie treked off to college or a new job), go join a team, or start one of your own!! The starting one is a lot of work, but the more you put in, the more you get out 
If you just mean over the summer, well relax, go to a few summer competitions, or do some fundraising 