I will start with a fresh thought here. I don't work on links (used to work in 2003-2004, with directories and blah blah, was fun that time).
How a link is valuated? There are three factors to it:
There is much to write about it but my concern is why will Google give value to a link coming from a old page.
Let me give an example, [ul]
say I am getting a link from XYZ.com/123.html (Which is 4 years old and with PR6) and
another pages XYZ.com/456.html (which is 1 day old and 0 PR) [/ol]
Most of us with say that Google will give value to XYZ.com/123.html more than XYZ.com/456.html, but WHY?
Isn't it more natural to add links while creating a page than adding links after 4 years? If Google hasn't done it so far, its time they check people who are editing their articles/pages to add links after X days.
If I was a Google engineer I would have given more value to XYZ.com/456.html than XYZ.com/123.html.
I also think so. There is good logic behind this. Without updating content just adding links on old page is not so good in the eyes of google. Its quite natural to add links with a newly created web pages.