Then you finally find a shirt which is just the "right" length at the store, and three washes later and it is too short... But you cannot buy the next size up since you need more LENGTH not shoulder width.
Very few brands make t-shirts which are 2x-tall (as opposed to 2x-large, where both the length AND width increases). A medium-2xtall would be like the unicorn of t-shirts.
The sizes should be: S, M, L, 2x, 3x, etc & S-T, S-2xT, S-3xT, M-T, M-2xT, etc.
There's a Dutch brand that specializes in extra long t-shirts: http://www.girav.com/ - they have Standard Long for men 1.75m (5.8 ft) to 1.85m (6 ft), Long Fit 1.85m (6 ft) / 1.90m (6.2 ft) or taller, and
Extra Long Fit 2.00m (6.6 ft) and over.
I'm a huge fan of Eddie Bauer's medium-tall shirts. They usually don't sell them in store, but you can get one online if you are looking for an option to try out.
It took me forever to find a fairly athletic fit (slim but not skin tight) in my height (6'2" with a long torso) that also doesn't have logos or random graphics (solid colors and maybe a pocket is all I want).
If you have a favorite choice it'd be great to know it and have more options.
*Full disclosure: I worked at an Eddie Bauer in college.
This is how military utility uniforms are sized: Small, Medium, Large and Short, Regular, Tall. I'm surprised that idea hasn't spread into mainstream sizing.