[boost] Removing old branches

I received an issue about Boost PP having lots of old branches which the issuer would like removed. I notice most other Boost libraries also have lots of old branches. Is there any policy about removing these old branches from a Boost library repository ? Many of these old branches are svn-branches, but most of them do not have any value any more and, of course, do not affect the current 'develop' or 'master' branch.