Quote: You may have gotten some good links in the past, but don't count on them helping you forever. Old links go stale in the eyes of Google. ...
Google's Matt Cutts responded to a user-submitted question asking if Google removes PageRank coming from links on pages that no longer exist (for example, GeoCities pages that have been shut down). The answer to this question is unsurprisingly yes, but Cutts makes a statement within his response that may not be so obvious to everybody.
"In order to prevent things from becoming stale, we tend to use the current link graph, rather than a link graph of all of time," he says. (Emphasis added) Reference: Ways to Get Fresh Links to Old Content for Better Search Rankings
There is a video of Matt Cutts
Google's Matt Cutts responded to a user-submitted question asking if Google removes PageRank coming from links on pages that no longer exist (for example, GeoCities pages that have been shut down). The answer to this question is unsurprisingly yes, but Cutts makes a statement within his response that may not be so obvious to everybody.
"In order to prevent things from becoming stale, we tend to use the current link graph, rather than a link graph of all of time," he says. (Emphasis added) Reference: Ways to Get Fresh Links to Old Content for Better Search Rankings
There is a video of Matt Cutts