@velox_vulnus T480 owner here.
Don’t expect T480 with i7 to actually run 4 GHz all times when needed. Get an i5 model instead.
I have i5-8350U. The best frequencies I could get on heavy load are 3.5-3.6 GHz (dGPU heatsink + PTM7950). Still throttles but not so much.
T480 has excellent battery life with both 24 + 72Wh batteries. What was the main reason why I got it.
My laptop wasn’t refurbished. I got it used without some parts - SSD and both batteries. Then I bought all parts by myself.
It could be cheaper to refurb it by yourself rather than by someone else.
@velox_vulnus no, there are no battery mods for 80 series.
It also has no CD/DVD that you can swap for 2nd drive or so.
I recommend you to watch a T480 review with disassembly first.