Lately, I've been noticing some of my girls seem to expend their oil and ammo tremendously fast, like, they only have enough for like 4 battles or so, and I'm wondering if it might be because they have a higher level than before.(or it's just me imagining things)

I thought it might be that, because I was also trying to figure out why would someone want to "lock" their level.

Does anyone know something about this?