Devils Advocate Rick.
What good is it to keep the posts if you limit the date range to search by.
When it gets so large the fulltext is slowing things down the only thing you can do is really search in chunks. That's what the newer than / older than selections are for on the search page. Having a 1 year date range doesn't limit you to only last year's posts. You can search any daterange, ie 2004-2005. It's not the optimal solution, but as the size of the db grows, fulltext will slow down.
