I got the Surface Pro X a few years ago purely for battery life, performance be damned. Great decision, and it fit my use-case perfectly. Maybe a little too perfectly for Qualcomm, because I have no reason to upgrade to something more performant when all I cared about was the battery life.
Edit: This recent push towards Windows on ARM is also benefiting these old WOA devices. Programs that would barely run before (because they were compiled for x86 and had to be emulated on a chip that could hardly handle all that extra overhead) are now getting native ARM version releases that run way better. In my experience, my Pro X’s performance has effectively been improving as time goes on, so I have even less of a reason to get anything new.