I would keep writing to them until they realise you are a "real" person taking surveys and that you care enough to keep insisting, that you've been accumulating all those points for a reason, etc. Hopefully you'll end up receiving something else other than all those nondescript e-mails they usually send.

Fortunately I didn't have too many points in my account but, for some reason, just before they closed it I received 2,000 points out of the blue... Really strange.