I've noted several times that my mimic seems to have issues when combining resting and logging.
Its happened about 10 times now, I'll end up resting, and logging shortly after. Relogging at a later time (sometimes 10-15 minutes later, or the next day), when I go to Mimic a spell, it says I've already copied that spell since resting. And it will do it for EVERY spell I try to mimic. Resting of course resets it...
So something amiss with the variables marking a spell mimicked or not, I'd imagine. Not -that- huge of a deal, but I've had many times now I go out with a group, and getting to the quest zone, I'm unable to copy as we start buffing, and what not, needing another rest, or what not.
Certain scripted stuff simply requires a fresh rest after you login. It's the price to pay for custom coolness, so plan for it.