If you can only get a middle E- seat now, by all means unseat yourself now. You have nothing to lose. But if you have an E- aisle or window now, do you want to gamble and be ok if end up with a middle seat? I personally would not trade an E- aisle seat for an E+ middle seat.
I don’t know for sure if UA status doesn’t play into E- to E+ op-up. But it makes sense since anyone with UA status most likely would not be in E- to begin with.