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And on that same topic, does linking to internal pages from my own home page, but only for a limited time, have any impact?
You get your link on a great page, the link is slated to remain there for 2 weeks...
google doesn't crawl the page your link is on except for once a month...
you come and go, the SE never sees it...
the short duration links/ I think would be hit and miss at best....unless you knew the SE would crawl that page during your presence... you would probably miss out on what you are really looking for..."the bump" from the page..
The idea being that once Google comes across a backlink pointing to your site the clock starts ticking. If it takes 6 months (for example) you'd only get a partial effect during this time, its full effect not being felt until the ageing filter has finished.
It would be a sensible way for Google to try to counter the effects of the sale of short-term links to boost PR.
once the link is gone so will be the "bump" on the next pr update.
And that is after the next "real" PR update -- the one calculated in Google's secret back end -- rather than a toolbar update. Real PR is updated continually, so depending on the crawling/indexing schedule for the linking page, any boost to the target page would vanish very soon after the link is removed.
See this Google Patent: Information retrieval based on historical data [appft1.uspto.gov] for some eye openers.