I've been using credits for years now. I recently tried a theme house addon called sub accounts. It seemed to work awesome on the development server, but when added to the live server we have issued with credits being synced between linked accounts via the sub account addon. Furthermore, you can't search by what accounts are sub accounts and thus, now I have to go through thousands of accounts and find the errors because sub accounts has no way of searching by accounts that are linked. I submitted tickets and PM's... I doubt there will be any resolve to this issue.