Just wondering if Google take into account the length of time a site has been at say the top position for a certain keyword when deciding on search positions? I mean if there was a site that had been the first search result for a given keyword for ages, would you be able to knock that site off the top spot if yours was SEO was better for that keyword, or would it take longer than usual?
I personally think it would take longer than normal. There are reasons why that website has been on top for so long. They likely have very strong, aged backlinks. If the rankings are jumping around, there isn't one website that is totally dominant over the others. Google can also look at factors such as bounce rate to determine if people are finding what they want on that #1 site or if they very often come back to check some results.
I believe there is something to what you're saying because some of the top sites in the niches I've chosen have been there for as long as I can remember. I guess it all depends on more than just the age factor if you're going to try to bump somebody out of the top spot.