This is something I've been struggling with too. It doesn't feel "fair" to miss some of my troopers each day, but without spending ironite, it's not always possible. I try to use the people I know first, and hope the others don't mind if I occasionally can only use them every second day. It's certainly much easier during events when you can farm Powerslave, or are already buying SoT refills.

What starts of a really helpful support system, slowly morphs into an anxious feel-bad pressure system. Increasing the 120 SoT limit would fix it though, no need for anything more complicated than that!