I will state which my fellow readers would not like to read.. The battery life on my 15PM is even worse than 18.1 Beta 2.
My 15 PM is at 97% health and 150 charge cycles. On 17.5, it used to last 1.5 days. Now on on 18.1 Beta 3, it is completely dead by midnight.
Happily, my 15 PM is in much, much, much better shape with b3 than b2. b2 was torching my phone, almost literally. Frequently too hot to even charge, sometimes too hot to hold, it would regularly go into super-heated mode. If I wanted to charge it, I would sometimes have to power the phone off completely to do so. The number of times my battery was sub-20%, sub-10% charge was nearly constant. It would die in the middle of the night. My battery health went from 99%/98% (can't recall which, now) down to 91% in less than two weeks with b2.
With b3, my phone is operating much more like it did with 17.x, or even 18.0. Nice and cool, responsive, and battery times that don't make me start examining every little thing on the phone.