From Scamtaku ask:

Question:

When do that limited items in peropero (pero shake and pero burger) ACTUALLY expire? Last time you guys said at the end of the last event so I used them all up, but we're still getting them (in current coliseum event gatcha and rewards) please let us know if we can actually save these up.

Answer:

We mentioned early on that the items would last throughout the current Coli event, and then would expire!

...

...

Just Scamtaku...