According to the wise words of one of my old teachers, "if your last achievement is more than five years old it is as good as obsolete, time to work on something new".
Makes sense to me.
What most people don’t realize is that achievement like any other thing has a life span which is usually not that long. Very few accomplishments have such a massive impact that their significance and magnitude transcends generations. As for the rest it is like a flower in bloom, amazing while it lasts but not worth much once it has wilted. So it is probably not a good idea for people to brag about some amazing feat they accomplished 25 or so years ago. Not only does it sound immodest, it also draws attention to the fact that they have accomplished nothing worth mentioning since then.
For those who have that ever pinching ambitious streak in them, they should know that one’s life should not revolve around one event, one goal or one accomplishment. It should be a constant struggle to excel, a desire to move beyond the point they have previously reached.
To continue to strive for better and beyond is true achievement.