Search Engine Roundtable reports that 301 Redirects Pass Google PageRank & Signals in a "Couple Weeks". SEOs and Webmasters have always queried about the time taken for a site to pass along a PageRank value from one URL to another via a 301 redirect.
Google's Adam Lasnik responded via a Google Groups thread, saying that it takes only about a couple weeks.
301s pass PR and related signals appropriately. Usually takes a couple of weeks for things to smooth out, though.
Search Engine Roundtable says, “I was a bit shocked by the statement of just "a couple of weeks" for 301s to "pass PR and related signals appropriately." I always thought it was a couple months or more. Well, maybe Google picks up the changes within a couple weeks. I.e. the time it takes to crawl the new information and URLs. But maybe by the time all this data is processed it takes longer?”
Adam Lasnik has responded to this general query, however what really did he mean by 'things to smooth out' is still not clear.