I've never seen a laptop actually survive longer than 7h practically. The advertised battery life may say >10, synthetic benchmarks may say a bit lower. But once you use it with wifi on, with proper brightness, actually doing some work - no - it always takes a big hit.

Did you try windows, or if linux with lightweight use, would it improve the battery life? I had a macbook pro for 4 years so battery degraded and the processor wasn't that efficient but anecdote for newer macbook rarely reports anything less than 6 hours. I'm interested in a X270 (for the battery) but then I read somewhere battery on linux is kinda unstable. What do you think?