I understand what Rich is saying, either which way you turn, someone is going to be upset.
I am at a disadvantage in offering up any other realistic solutions/ideas for a win-win then. I don't have any historical track record for memberships (adding or losing), I don't know the cost vs. benefit ratio for behind the scenes programming, nor do I know actual traffic patterns, etc. So basically I can only offer up "surface" type suggestions and give my own experiences.
I own my own business, so I completely get it. For all the "already thought of it or tried that" suggestions I get, every so often someone will sneak in a "winner" of an idea.
If something else comes to mind, besides the "expiration" idea, I will be sure to bring it up. I feel vested in the success of this site (that is how successful sites make users feel), so when I offer up ideas, I do so with the best of intentions and never to point fingers or cut people down.
Again, great site, and I will see if my little brain can think of a cost effective happy medium solution.