Yes it is possible if the number 1 article keeps improving for the search quiry intent
as your site continues to age, it becomes much easier to maintain number 1 position. key is here not to do crazy shit where you end up hurting yourself because of the never ending google updates
the quality of links are all crucial.
Yes. But you have to keep a track of your competitors' sites. They may also try to rank in first position.
If you are ranking for a long tail keyword that may not be commercially relevant is will be easy. Most lucrative keywords have been taken up, although there may be enough that remain. You need to find those keywords, but again once you find them and rank for them, someone else will start ranking for them.
After that amount of time, it's definitely possible to get to the first position in Google, with a lot of effort and work on site optimization, its fast-loading, navigation, structure, implementation of quality keywords, adding relevant backlinks on the site, and so on.
