Board Thread:Game Discussion/@comment-5996974-20130613122758/@comment-10214922-20130613141947

My observations if it helps:

If you're goal is farming cubes/getting top rank, upgrade prior to event. Upgrading 4 or 5 cards on day 1 is a huge waste of time. This is expensive.

If you're short on medals then level during event. Generally if you're short on medals it's because you are new to the game (first time players need to MTM 9 cards, then the more you play the less cards you need to manage per episode). Also if you are short of medals it's because you haven't been playing at a high tier (you control the pace of bosses, therefore the rate of medal gain), so you probably don't need to push hard on day 1 of the next event if you are not highly competitive (generalization).

If you're short on space then upgrade fodder cards - but this is usually better to do during an event when you have a chance to boost your deck with an X3/X5/X10 and storing upgrade value in anticipation of upgrading rewards. This is also expensive.

Mostly, it depends on what your next episode goal is but you need to think about it going into the tail end of the current episode.