For my newly registered SEO spam domains I check them daily until it gets boring or until the traffic is at a relatively steady stream or until I forget about them (which happens quite often). Then I just let them sit there and let the search engines decide on what to do with them... so far I am quite content with my findings about the search engines and the domains work quite well considering the fact that setting up one domain takes considerably less than 1 hour (registration and DNS stuff included).

Other server stats besides visits and how many files a "visitor" pulls I do not check (or even track). I just see that if a visitor pulls lets say 8k files it must be a bot... once those massive file-pulling ceaces its pure visitors... Then I check google and query for how many files are in the index... I do keep track about how many files are on a given domain.

So I guess I did not quite answer right but it was an urge to tell

EDIT: oh and I keep track about what users where searching in the serach engines