Google's John Mueller once again confirmed that Google will continue to retry old, redirected URLs for years and years even if the redirect remains in place for a long time (a year). John said on Twitter "I suspect we'll keep retrying these for years, on and off."
John added that the crawling of those URLs will slow, he said Google will "significantly slow down crawling of things like that, but slow crawling of many URLs is still some crawling." John added that "it doesn't cause issues with the rest of the site's SEO."
So even if you see Google trying to access these old redirected URLs, you are probably not in bad shape SEO-wise. It is just something Google does with its big long-term memory.
We have a long memory. I suspect we'll keep retrying these for years, on and off. In general, we significantly slow down crawling of things like that, but slow crawling of many URLs is still some crawling. It doesn't cause issues with the rest of the site's SEO.
— 🍌 John 🍌 (@JohnMu) August 12, 2021
Forum discussion at Twitter.