> Helping spiders find your new home. Matt Cutts once said that redirections can lead to loss of value (think about it as travelling extra distance), yet 301 should be an exception.
The point about 301s is that the search engines SHOULD learn from them
and update whatever stored URI they have that sent them there in the
first place. So you should only ever see one reference to a
301-redirected URI once for each search engine. Once all the search
engines have been once, there should be no other attempt to spider that
page. Of course, there may be manually stored copies of the URI in
other people's web pages and bookmarks, and a search engine picking one
of those up may come again.
I've decided it's best to leave 301s for old pages up permanently. I
still get occasional references to URIs that died five years ago.