I agree they would be less effective as they wear, but i've run my LTX/AT's (not the AT2) for 80K+ miles. i think into the 90's but that sounds like a lot so i must be mistaken. and i agree with you about my scenario too. it's a tough "one tire" situation.
there is a lot of good info on the AT Tires thread i'm trying to digest as well. The Cooper AT3's are rated highest by CR with Michelin AT2's second. CR classifies the MS2 as "all season". that worries me. it says to me that they are on the "lighter" side. Another thing is, i don't like chains. I mean, I like them when i need them, but i don't like needing them if i can avoid it. I had a place up in the hills years back where i had to chain up a lot. it's good to have them, but i'd rather have traction and stay in bounds and only use chains when really needed. btw, i am assuming we are talking "real chains".
well i feel like i'm getting closer. thanks to you guys... keep the comments coming. i haven't decided yet!