lucy24 - 9:41 am on Mar 23, 2012 (gmt 0)
If you use 301's, Google will eventually forget about the old URIs.
For a given definition of "eventually". I finally put my foot down and slapped 410's on some pages that I moved and 301'd a full year ago. Redirects are nice for humans who have old addresses bookmarked, but it's infuriating when search engines keep eating 301s. What do they think-- that you'll move back, but not bother to put in a single link to the old/new URL?
Honestly. Even the post office only forwards mail for 6 months.