Hi there, I have a question: How long should a backlink be alive, in order to be considered by google and calculated in the page rank algo? 1-2-3 months?
IMO The calculations start as soon as Google finds the link but adds more value the older the link gets.
yep, generally google will count the link right away, however you won't see a noticible PR update from it until they do one of their toolbar updates. you can see a PR update history here: http://www.presentationrentals.net/google_toolbar_page_rank_update.htm
I agree, And, when is "as soon as Google finds the link" ? Usually old pages with changing content and high PR are crawled daily, but newer pages (with low or Zero PR) can be crawled only once a month.
As soon as Google finds the link they are calculated. I think the full effect of links take a few months.....this prevents people from adding links for a quick boost and then removing them