I have an X1 extreme. I’ve never gotten it to last over 2h on Windows. On Linux it can last an hour or so more if I turn off the NVIDIA GPU, but otherwise it’s still abysmal.
Then there’s the stupid BIOS warning that requires you to press ESC for the computer to boot if it’s not plugged in to the official charger, which means that if it ever reboots at night it’ll just keep you awake (because the power management hasn’t been initialized yet so it’s stuck at 100% CPU) until you go press ESC.
Oh and it thermal throttles all the time so the CPU performance is good for a few minutes and then it’s just awful.