FWIW I have a t480s with the 1440p display and am using Linux and my battery life is typically around 6 hours or so for regular use. If I start running more dev tools and building things it plummets as to be expected, but the display really doesn't seem to make much difference.

The biggest thing I miss from my MacBook is being able to open it after a week of being closed and still have battery. There's definitely something not going into deep sleep when I close the lid, but that's probably my fault.

To use no battery when sleeping, you'll want to configure hibernation. I haven't done this because I only suspend my laptop for 10-12 hours at a time. Also it's tricky if you're using disk encryption with a swap file.

The Arch wiki has lots of information on how to do this: https://wiki.archlinux.org/index.php/Power_management/Suspen...