A few trips around the sun. That's all we get. On average, you'll get about 80; maybe if you're lucky you'll get 100. Some people are given a lot less. We really don't know how many more we will get for sure. Many people worry about making an impact in that time, or about their legacy.
But really, no one ever gets to know their legacy. No one can plan it, orchestrate it and/or claim theirs is better or more impactful than anyone else.