In this wikipedia article, it describes protoplanetary nebula as "short-lived," but I'm not sure in relation to what? This could mean billions of years in some contexts.

How long is short-lived?

Bonus if there are any useful rules of thumb in astronomy terms for future uses (how stars timelines are described, versus galaxies, etc.)

In this wikipedia article, it describes planetary nebula as "short-lived," but I'm not sure in relation to what? This could mean billions of years in some contexts.

How long is short-lived?

Bonus if there are any useful rules of thumb in astronomy terms for future uses (how stars timelines are described, versus galaxies, etc.)