Similar with my Surface Pro 4. After a couple years of casual use (it was my "browse on the couch" computer) the battery was significantly degraded. I think a

Similar with my Surface Pro 4. After a couple years of casual use (it was my "browse on the couch" computer) the battery was significantly degraded. I think a big part of the problem is that "off" doesn't necessarily mean "off". If you just do "Shutdown" from the menu it is just some kind of suspend or hibernate state (I'm not sure which...PC hardware and Windows have a bunch of different "not fully on" states). It's still doing stuff that uses power. It's also doing periodic things like automatic updates. The net result I believe is that even though from my point of view it was only being used occasionally, it was actually going through a battery cycle almost as often as if it had been my main computer. I haven't used Windows in a while so don't remember all the details, but I think if you hold shift while invoking "Shutdown" it shuts down more than a shiftless "Shutdown". There are also command line commands that will shut down even more. I never did find a way to shut it down enough that I could not use it for a week and still have a usable charge on it. Hey, do you have occasional problems with disk encryption? Every so often when I open it I get some obnoxiously bright screen telling me I need to enter my Bitlocker recovery key. But if I cancel that it goes ahead and boots and has no trouble decrypting the disk.