I would say the Superchip would have no adverse effect on the life span. The shift points are at a slightly higer RPM with the chip, but they are also quicker & slightly more crisp. I have one with my ATX & I am quite pleased with it. It took a little getting used to, but when I'm having fun with some spirited driving, it is well worth it IMHO.
Firmer shifts = less clutch slip = less wear on the tranny clutch packs.
That's how I see it, and the tranny experts will soon chime in and give you a definative answer.