Board Thread:LOC General Discussion/@comment-108.35.154.66-20130911165857/@comment-76.79.134.150-20130917205156

one way can help is change the amount of pp an account can hold base on it's level. For example level 10 account can hold 99pp, but a level 200 account can hold 9999pp. That way suddenly having your high-level account being banned is not a laughing matter anymore, and you can't easily xfer ill-gotten cards/pp/eds to another alt account since they can't hold all that stuff.

And obviously, put an expiration date on refused/expired trade, like say 1 or 2 weeks. If refused/expired trade isn't claim it is lost forever (the game can throw up a warning message 1 or 2 days before the destruction)