Older sites are not keeping their current ranking

Patience, that is never in any human. We are happy that, our site has a good ranking in google, without  any changes in the last 10-12 years, it is good for our site and we mean that we are done best SEO efforts for that site.

But today, time is changing, strategy change and also google algorithm is also changing, because google is very serious about  their result. As it is not possible for all sites, especially for who are not serious about their site search.
Matt Cutts, Google’s head of search spam, posted a video and statement about site search, why some old sites may not have their ranking in google last forever.
Explanation by Matt Cutts on Older sites are not keeping their current ranking.

He has also explained that there are many old sites that are about 10-12 years old, well it is good things, and some of these sites have their original design templates and have not done much to their sites to improve things over the years. Among them, they have never redesigned the site,  never updated the user interfaces, as well as never added new features for their users, etc.  And, today in this competition period, if you want to stay competitive, you need to take a FRESH look on your site and always keep upgrading, modifying,  improving the site and the user experience.
However, we all know that new and upcoming sites that have a better user experience, may exceed you.  But the  moral of the story is, having an older domain doesn’t mean you will always keep the rankings that you have today and will be tomorrow.