Ive noticed that sites older than 5 years have special authority. Now it may just be because they have accumulated the most backlinks, but many of these top sites aren't totally optimized for the keyword via their site or backlinks. I think for best results you have to expect to wait 5 years for the best results possible to compete for the top or at least bust your butt for a couple of years to make up for the disadvantage. You don't need a 5 year old site to rank in the top 10 but it certainly is an advantage.
till now I always bought domains for 1 year and this is not right thing to do! Easier sandbox and lower ranking for sure, from now on I will buy for 2 years
I think this depends on how competitive your search term is - I optimised our own site for "website design bury st edmunds" when we moved town, but every seo improvement I made Google gave us a serps boost for a couple of hours and then knocked us back to no 9 for this term. This went on for 4-5 months and then, suddenly, with no further seo changes we suddenly started climbing the serps and are now no 2. I also saw another one of our sites get a boost up the serps at 1 year. I don't know whether we were sandboxed or just had a filter applied; I do know time was a factor.