Know that the most it can go to is 12GB.

If you want more memory you have to go to the T4XXp series, and probably buy the RAM yourself as the premium charged is considerable: 16GB on NewEgg is $120, while the premium payed for 16GB out of the box is $340. The T440s also maxes out at 12GB.

Just don't buy the RAM from Lenovo. On my T430, access to the RAM is a screwdriver away.

It's a bit of a pain with the T440s (have to pry apart all the plastic), but still better than paying what Lenovo wants.

I did this. I had an X1 Carbon, but couldn't find a way to upgrade the SSD (it's some weird size and connector) and 8GB wasn't enough, so I sold it and bought a T430s.