Keep 301 redirects in place as long as possible
Although Google are able to recognise a site move as a permanent move which doesn’t require the redirect, although some links may not remain completely redirected.
Image Re-Crawling Takes Longer After a URL Change
Images are not crawled very frequently, so when you migrate them to new URLs/domains, it will take a lot longer than pages, perhaps months.
Avoid Redirect Chains
If you change domain and URL at the same time, you can have 2 redirects in a chain, although redirecting directly is preferred. Google can follow more than 5 redirects in a chain, but in separate crawling attempts.
Disavow Backlinks on New and Migrating Domains
If you migrate a site to a new domain which has unnatural backlinks, you should disavow the unnatural links on the new domain as well.
Migrating Domains Can Result in Some Loss of PageRank
When you migrate domains, the full authority is not passed, a few signals may not be carried through which could result in a small drop in performance.