8.04.x, 10.04.x, 12.04.x, 14.04.x, 16.04.x all LTS. anything else isn't.
12.04.1 isn't necessarily more stable than 11.10. look at all the graphics driver bugs and whatnot. "more stable" could mean lots of things. what doesn't crash with the current fglrx driver for one, latest security patches for another, etc etc. you can't quantitatively say for sure X is "more stable" than Y