how long does a tardigrade live?

This looks like a fascinating subject! According to this article: “without dormant periods a tardigrade would live for less than a year”, otherwise they “might well reach the ripe old age of 60 years.”

This NASA article describes how tardigrades can “dry up into the little barrel called a tun”, allowing them to survive extreme conditions for long periods of time. For example: “live tardigrades have been regenerated from dried-up mosses more than 100 years after they were collected.”