good idea~

I've been saving mine for the actual Kage Treasure.
I want to get the Mizukage :D
Basically newer Treasures will have better ninjas.
Kages > Sage Naruto > Pains
^ Somewhat like this lol though depending on how you make your teams...even Pains can beat on some Kages/Sage Naruto comps.

Pains will become even easier to obtain once "new" ninjas come out. Pains will appear in event even more often. There are supposed to be 1 or more Elite Instances with Pain so you can farm 1(at least).

all F2Ps and low spenders are better off saving for Kage Treasure at this moment. Especially lower level people. You don't want to get a few Pains then reach max level and fight full kage teams. You want to reach max lvl and have a chance against those people with your own Kages :D I'm trying to save up at least another 100 seal scrolls. Hopefully Kage Treasure waits another month at least or 2.