That phenomenon has a name and a Wikipedia page (probably called "X's Law") but I forget what it's called. But the point is: the longer something has been aroun

That phenomenon has a name and a Wikipedia page (probably called "X's Law") but I forget what it's called. But the point is: the longer something has been around, the longer you can expect it to be around (given that you know nothing else about it). Cf. the age of a mountain vs an individual butterfly and your prediction of how long you expect it to be around for.