How long to leave up the redirects and the site change in Webmaster Tools?
JOHN MEULLER (Webmaster Analyst from Google):
Essentially a 301 redirect is a permanent redirect, so theoretically you’d keep that there indefinitely. Practically, we try to crawl all URLs on a site within a reasonable time. Sometimes that takes a couple of months, sometimes maybe half a year or a bit longer. So if you’re looking for the minimum time that you need to keep these redirects in place, I’d look at something maybe twice as long as the technically minimum time. And at least keep them there for a year. So in a case like that, we can definitely see those redirects. We can definitely follow them. We can cache those redirects. And if we recheck them again after a while, they’ll still be there. So I’d at least keep them there for a year. If you can keep them in place longer, that’s probably a good idea as well.