Board Thread:Questions and Answers/@comment-35518455-20180731182051/@comment-35353971-20180801014103

Never sell dupes. In the long run, that extra stats, that one push past the enemy limit will in the long run help more than the XP. You can actually get more than twice as much XP from the stage “Merciless XP!” if you use an XP up, than from selling an uber. It also takes more XP to level an uber up from 29-30 than you get from selling one, so by using it you're also SAVING 500,000 XP whereas selling it is a waste in the long run.