It used to be that the blue's had a life of about 20k hours but nowadays the blue is more like 40k hours and the other colours much higher. It depends if you go for a decent display or not... Depends on price a little bit.
Anyway, what's wrong with a dot graphic display? who doesn't like a bit of retro? 
For temperature you could just use a 20x4 display and use some 4 line text for BIG NUMBERS...
Mowcius