It really depends what ecosystem you are in. For example, the nodejs/npm ecosystem is on a never-ending cycle of package upgrades. If a maintainer is not maintaining a package, it will eventually have to be replaced for one of the following reasons:

1) One of the package's dependencies has a breaking change which breaks the package

2) One of the package's dependencies has a security bug. The dependent package cannot be upgraded to a fixed version because the dependent package's fixed version has a breaking change which breaks the original package.

Basically, ecosystems which do not have strong backwards compatibility tend to require packages/libraries/creates/assemblies/DLLs to be maintained forever.