When I change domains, how long should I leave the redirects in place?

If I get a new domain and want to 301 redirect www.old-domain.com to www.new-domain.com, how long do I have to keep the redirect up before I can start using the old domain for something else? Just until it has been crawled once? Jacob, Denmark Russian subtitles provided by Mike Shakin. Have a question? Ask it in our Webmaster Help Forum: http://www.google.com/support/forum/p/Webmasters?hl=en Want your question to be answered on a video like this? Follow us on Twitter and look for an announcement when we take new questions: http://twitter.com/googlewmc More videos: http://www.youtube.com/GoogleWebmasterHelp Webmaster Central Blog: http://googlewebmastercentral.blogspot.com/ Webmaster Central: http://www.google.com/webmasters

Comments

1. i redirected properly from old to new but your webmaster shows 1000 of links from my old website i used disavow tool too, But you removed my website from search rankings and gave me site wide match pure spam this is real bad :( it hurts a lot, how 301 redirect will become as backlink? please solve my problem
2. Like to know, Can you remove 301 redirects files, that are no longer in use from your server ? If so how long would you wait for ? :-) 
3. 301 on page level? Are you kidding? The site I maintain has thousands of pages. How do you get around that? Category level?
4. I moved a site over from blogger to wordpress and it seemed to work fine except instead of redirecting to individual post it redirected to the home page. So now all my links show up as Intermediate Links to my home page. I fixed the problem but I was wondering if google will crawl the old site again and automatically correct the problem or am I now stuck. The site took a major hit in the search engines first with Penguin update and now this any help would be appreciated.
5. Dub-Dub-Dub!! :)
6. Yeah dub dub dub is interesting way :)
7. Now, I lost all my positions in google. I made 301 redirect and every position vanished. I've read on forum that positions can come back after 6 (sic!) months . Don't redirect if you don't have to. There also might be a problem, bacause I redirected from mysite.pl to mysite.eu(slash)pl. It really sucks, because this was my main client source and now it's very difficult to make enough profit.
8. Hello Matt I have a problem. I made 301 redirect from mydomain.pl to mydomain.eu. After a while all my traffic moved from pl to eu. I have a few high ranked keywords, some of them on first position, but yesterday, I can find only 3 keywords, on positions 70, 80. I don't use black SEO. Is this permanent, have my website got filter and how i can check this.
9. It's very important that you never give up the old domain. Because the you're able to 301 all incoming link from the old domain to the new domain. If there are any. And maybe someone bookmarked the old domain. So I would keep the 301 for years and look into my Analytics for old 301's from the old domain, before I skip the old domain or use it for something else. :-)
10. I have to agree with Porretz and ianvisits; Search Engine "Awareness" isn't the whole story; any existing link juice you have has be be maintain/curated. That said: assuming you maintain ownership of the old domain and redirect things on a page-level rather than a site level, the question doesn't matter; a correctly-formatted 301 will pass the juice where you want it/it belongs
11. The simple answer should be "as long as possible" as you are not just talking about Google search results, but clicks-in from outside websites that linked to content on old-site.com and they wont know you changed your website in a way that breaks their links.
12. Is there any penalty for old 301's? That wasn't addressed in this video, but I can't see a reason to take down a 301 redirect on a page level (domains are another issue).
13. haha.. is that the fastest someone has ever said dub-dub-dub?