How long before images lose signals after a flawed url migration?

Glenn Gabe publishes his findings on what happens when you don’t consider images in your migration and explores things like how long before images lose signals after a flawed url migration?

He unpacks his findings when a company decided to move their images to a CDN, but forgot to add 301 redirects from the old urls to the new ones.

For this site, quickly reverting the migration (only a few days in) yielded excellent results. Rankings jumped back across both image search and web search.

PS: remember this applies even if you are going from HTTP to HTTPS  for images.