I have a somewhat older T4xx model that's still running (bought in 2012/13 I believe). During its lifetime I upgraded the hard-drive, RAM, the keyboard (well, it wasn't an upgrade...coffee spilled on the previous one...) and even the screen.

I have since upgraded to an X1 carbon which is significantly slimmer and lighter (although I never had any complaints about the previous laptop in that respect).

I personally think the T4xx line is a perfect compromise between portability and power. So as long as you're ok with having a slightly thicker and heavier laptop you'll be very happy with it.