Is there a thread somewhere on the web that lists the cookie life of prominent Sponsors?

While waiting for the 2012 election to get over, so customers can get back to having time and attention to buy our on-line entertainment, I'm housekeeping Sponsors that I am an Affiliate of.

I've read here over the years that most Sponsor cookies have limited life. It's obvious when I go over my Affiliate tracking over the past 7 years, and see peaks and valleys. While it is a nice advertising slogan that as an Affiliate I can have members for life, what is the measure of that life?