I suspect the opposite, actually. The T42 I paid for myself and cared for like a baby, until I heard from too many people that it was built like a tank, and started treating it as such. The MBA was originally an employer-supplied laptop, and thus was unloved from the start. It fell to the ground many, many times. All the corners are dented in, and I once built a computer ontop of it without realising (which then dented in the lid, and probably resulted in the crack in the screen).
I powered on the T42 recently. Such a beautiful machine. Shame fixing the screen hinges requires so much disassembly. I have very little chance of doing it correctly, and the value of the laptop is so low now it's not worth paying someone to do it for me.
Sadly, I'll probably end up buying a macbook pro when the next refresh comes through. Too much friction changing platforms again.
Also you can watch how the markets values second hand laptops, generally you will see that second hand thinkpads retain more of its original market price then second hand any other laptop.
Having said that thinkpads usually do not have the best screens - but even though its slightly brutal to not have a good screen anymore, I am more comfortable with the fact that I do not have to worry too much about my laptop not working or overheating.