In my opinion, if Trump thinks that any subordinate is not doing a good, that subordinate is just dumped. Anybody getting moved to another job, is likely being sent as a troubleshooter, based on a good assessment in their last assignment.
In the case of Rick Perry though, he might get special treatment, because of his unique value with the big oil money, and hard core conservative donors.
Department of Energy is a bit like EPA - stopping them from doing things is the real measure of success.
Excellent points by both of you...