isn't there any way to consolidate the PR that you have achieved ? I mean after some time doesn't google have an algorithm to consolidate the PR to some level so that it doesnt fall too sharply just because some sites stop linking to you and you still maintain the good content.
PageRank is a measure of the links to your site ... so why would they want to freeze it so it's not affected by links anymore? Or are you saying peoples' PR should be able to go up, but never down?