My password tool shows me which are oldest. So, quarterly (on tax day) I also make sure to change a few of them.
One case I know is that in one system my old password was hashed with an older method (which was the right choice at the time) and when I reset I'm now using their updated (right choice today) hash.
Another feature is that services I don't use I'm reminded to close/deactivate.
And if we accept that most people don't use unique, never-before-seen passwords and that a password has been included in a plaintext dump, rotating passwords periodically doesn't even protect from password spray attacks, since someone has likely used that password before and you'll still be vulnerable.
How strong is that nowadays? How many bits of entropy?