I am not a "member" of your organization as far as I am concerned. I thought you were doing good work, so I sent you some money. That was not intended to be construed as a desire for permanent lifetime membership, nor was it intended to commit me to sending you as much money again next year -- much less the increasing amounts every year that you seem to believe yourselves entitled to. It *certainly* was not intended as a request for letters trying to guilt-trip me, nor for patronizing notes about "did I forget?" Such things do little to endear you to me, nor to ensure future donations.
Kindly pay more attention in the future, and do not over-interpret my gifts. They are exactly that -- gifts, nothing more. Attempts to misconstrue them otherwise will send my dollars to some other deserving fund, of which there are plenty.
(Which I suppose isn't as true as I would like -- a remarkably large percentage of charities play this irritating "membership" game these days. And it's not even fun to watch the plaintive letters pouring in, the way that it is to watch my TV Guide subscription expire. But I'm getting rather fed up with it...)