Feat seems fine.
But maneuvers all have refresh mechanics that allow them to be potentially used with no limit during any encounter as long as you can keep refreshing.
Potentially yes, but it means that hopefully you have an idea of what defines an encounter (at least at your table). 
You got me, thanks to recharge mechanics I don't need to define encounter duration when playing with maneuvers. If the player wants to use them again I can just tell them to use the recharge mechanic and since you can use those in downtime you just happen to start every battle with them!
