Jim, I hope you consider the "Update button" to compare version (Like rctneil suggested), just pointing to a page where the updates are won't help all users. If you ask people which version of Windows they use, they don't know!
Maybe in these early betas you could make use of your "Beta has expired" and change it to 2-3 months, and make a one time pop up that "This version is old, do you wanna check for an updated version?".
This way atleast people will get a notify that this version isn't final...