As far as affecting the SSD lifespan, I don’t think you’ll really be saving much, if anything, by not going the clean install route. On a recent Win 7 clean install up to SP1 and all the programs I wanted, SSDLife still estimated 99% lifespan which was something ridiculous like 10 years left.
It will be interesting to see how it goes for you. I just don’t recommend it for exactly the reason oliverredfox points out where systems have odd stability issues along with bringing over crap into the install that is no longer necessary.
