Let's say if some one has Ubuntu server 12.04 should he reinstall and put 16.04 or just update the security updates??? This is just an example.
I want to hear more opinions on this. What is a normal thing to do. I think there is no more linux servers online serving a website with ubuntu 8.04. It needs to be reinstalled at some point. Maybe it's not reinstalled? Maybe it can be upgraded? What is the standard procedure?
Ubuntu 12.04 reached it's End of Life at April 28, 2017.
So the answer is: the some one needs to upgrade to the next version (which is not the same as installing security updates) or reinstall.
If you don't want to reinstall, an Upgrade from 12.04 to 14.04LTS is supported and should work well. But be aware: Most installed packages will receive an upgrade too which might break some things.