Question

How long can a URL generate a 404 status code before it starts to lose the authority it used to have? Scenario: A site was overhauled and all of the URLs were changed. Most of them were redirected but I'm just now discovering that a number of URLs weren't redirected, and now it's 7 months after the site was overhauled.  

Answer 1

Do the 404 URLs still rank for anything in search results? If not they are probably not being treated seriously by the search engines.  

Comments

That's a good point. I'll check in search console.