With all this said, I still think that somebody has a switch they flip.
I have about a dozen "money sites" in 4 main niches. I do about the same things to promote them, and they are all "of an age".
The one that G really loves the most is in a specific and more unusual niche, and I've worked very hard on the look and feel. Call me whatever, but I don't beleive it's all about links. I have other websites with more links, though I haven't gone through to count up the exact numbers of higher PR links vs lower PR.
Or maybe it is just that the better and more "unusual" niche attracts more links I don't even work for.
Don't know.... It just confirms my final analysis, that you just need to do everything (or get it done) you can as well as you can.