Simple answers ....
1) This started here: http://www.mattcutts.com/blog/2006-p...-site-reviews/
IP doesn't matter.
Google wants to know if you run spam sites. Even if they're on different servers or different IPs, they'll still probably be able to associate you with them, if you have them.
2) How long you register for may make a .02% or .01% difference in your ranking, but not much more. Best just to register important sites long-term for safety.