There’s no way to get rid of the need to store pristines at this point. It’s been talked about but it’s actually not an easy problem to solve because there’s so many different use case situations that would be presented by removing them optionally.
With 1.7 the pristine storage was changed and in some cases you may actually see the situation as worse than before 1.7. Pristines are now stored in files named by the hash of the pristine. So if you have multiple identical files you won’t have duplicate pristines stored. However, we also don’t cleanup pristines anymore. So they just continue to build up. You can trigger unused pristines to be removed with svn cleanup.
There is a point to keeping unused pristines around, if you’re switching between branches we no longer have to download things that you already have the pristine for in 1.8.