Nobody knows how much time we have. But we can guess.
Lots of laws say you're an adult when you're 18.
Demographics and marketing experts think you're useful until you're 65. After that, you're done.
18 to 65. That's 47 years.
17,167 days (give or take a leap day).
So you get almost a billion and a half seconds.
More if you're under 18.
Fewer if you aren't.
And guess what? You spend 1/3 of those seconds asleep.
Now you have a billion seconds, more or less.
You now have a guess as to how much time you have.