[Neus]

I dunno, the popular idea that I remember is increasing their maintenance costs by 1 FP per 5 levels. So at level 30, it's 11 FP per round per Youkai, at level 60, it's 17 FP per Youkai.

I really dislike the Momentum suggestion because it means Summon Storm = I can't even unsummon my Youkai.