I just noticed that Mind Control only lasts for three actions maximum.

This seems to be a maximum amount, regardless of who, where, how, etc. In other words, no matter the psionic strength of the psion or the weakness of the target, they get at most three commands to a single target.

I assume it's per target, as only three total Mind Control actions per encounter would be even more restrictive.

I'd seen this before, but didn't realize that there was a limit of any kind. I suppose this is probably for the best, as it can be really frustrating to be Mind Controlled for much longer.

Anyone ever dealt with Mind Control before or used it in your games?