Board Thread:Questions and Answers/@comment-24212208-20150401114609/@comment-26131865-20150502180313

Save them. ALL.

When you will try, as me, to level up your rank (to unlock lvl 30 of rare cats, special cats ...), you will reach a point where you have no cat left to upgrade. The more cats you have, the more levels you could upgrade, the highest rank you could have, etc. Never exchange any cat with XP... you can have XP by many other ways, as week-end stages.