FWIW, I’m a Wink user (lurking as I consider switching to ST) and this has happened to me 2 times in approx. 18 month. Same basic scenario; App reports 97-98% battery one day and out of the blue the lock goes dead the next–a bad situation for me since the house is 600 miles away. Wink support said the fixed it as part of an update (twice) and mentioned that it might be an issue with the lock itself and that I should contact Schlage if it happens again. On course I’m well out of warranty.
Just checked the battery level using the Wink app and it currently reads 97%. Batteries were changed the last time we were on site in Late December. Lock was used perhaps 6 times when we were there. Battery level was still 100% when we left on 1/5/18. Lock hasn’t been used at all since and battery dropped 3% in 16 days. Doesn’t bode well and I suspect the lock will go offline within the week. Not fun problem for a remote installation.