It took seemingly forever for my P2 to recover a better battery life after the 8.1 update. But I plug in at 10pm everynite and after hitting 100% about 12am, unplug, go to bed, lose 7% overnite but don't replug till the next night at 10pm again. So since my charging habits remain the same it is easy to see how my battery has finally improved from that juice sucking update. Usually do about 4 hr SOT and am left with anywhere from 30% to 40% when I plug in for the nightly charge. I can't complain about that.
EDIT: I don't even see google play services listed in my list of apps using battery. I'll watch for it tho.
Shows 0% battery useage for the past 12 hours.
@zorro could it be that particular phone has a lot of stuff that requires GP services? I don't think I have that much at all.