If you have Google Juice, owning a domain is forever

Interesting tidbit

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Read the full story: http://www.forbes.com/sites/markgib...omain-name-is-forever-if-it-has-google-juice/

 

... and if you end up redirecting your old domain to a new name, be sure to plan out what method you choose. It should be a 301 redirect of course but Google recommends that instead of doing a blind redirect (eg: all traffic is now routed to the new domain) you instead do page redirects to help preserve your ranking.

Source: http://support.google.com/webmasters/bin/answer.py?hl=en&answer=83105

If you are redirecting a low ranked site without much traffic then personally I wouldn't worry about doing a per page redirect since you really don't have any ranking to worry about but if you were to take over a well aged site then do it right. If you are redirecting a site that has achieved sitelinks in the Google search results, then it will definitely benefit you to plan out your redirects carefully.