In my experience with recent thinkpads, my battery life never really beats the w10 install it comes with. Not sure if there are some very clever windows-only optimizations or what, but that's what I've noticed.
When my X270 was new I could get about >20 hours of battery life out of it on Linux with programming and light web browsing (e.g. Hacker News, etc.) It's a bit less now that the batteries have worn a bit, but the other day I accidentaly forgot to turn on the power socket while working all day and I didn't even notice until the next day.
I never tried Windows 10 (although I'm kind of curious now), but I think this is pretty impressive, and at these kind of levels a bit extra battery life is still nice, but hardly critical.
I never tried Windows 10 (although I'm kind of curious now), but I think this is pretty impressive, and at these kind of levels a bit extra battery life is still nice, but hardly critical.