The old ones had hot-swappable batteries (a second internal battery - of decent size - kept the device going while you replaced the external one). I used to keep a couple of extra 50 Wh batteries in my backpack and therefore had excellent battery life. The power efficiency wasn't great though.

I now have a Z13 Gen 1 (AMD 6850U) running Fedora and the battery life is passable. It draws 7-8W at idle from a 51 Wh battery.

So the battery life wasn't excellent.

My laptop can go on for days as well as long as I plug it in to a power bank. I just need to lug them around, defeating the purpose.