My guild is facing the same thing. We decided to find a larger meeting place and raise our dues $5 more. While we are finding many great meeting places to lease, non have a private large storage area for us. That is the biggest issue.
I guess you would have to have a waiting list and first on the list gets the chance to join when an opening is available. We have some paid members that seldom come to meetings and that is a problem when having a limited member list.
One more thing. If the membership stays the same it becomes stagnant and stuck. New members bring new ideas.