I am still seeing "new" Broken Links "linked from" pages that haven't existed since 2012, so I wouldn't hold your breath.
Google periodically rechecks old 404s, 410s, and old redirects... as it's a search engine and doesn't want content to be forgotten should someone change their mind. Google will recheck in particular when there's an update in progress, and that might be happening now.
I don't think, though, that this is the main thrust of the question. I assume these redirects were either for canonicalization or to get rid of extra pages that were dupes, and the poster is eager to know how long it wil take.
I recommend this thread as worth reading, even though it's from 2012... Domain 301 Redirect - How Long to Change the Index? Sept 2012 http://www.webmasterworld.com/google/4499653.htm
There's no one answer, as I think new index time depends on multiple factors, including when in the index cycle you've caught everything, the quality of your inbound links and how often Google respiders your site, and what kinds of complexities Google might encounter in making the switch over.
g1smd's summary is probably the best good-case summary in the thread...
New one should appear in days.
Old one can take months to drop out. This is not a problem.
But I've seen it take a few days or weeks to nine months... the latter in the case of a domain change many years ago during the infamous "sandbox" period. This nine-month delay is the type of thing one tries to forget ;)
Note that once you set up a 301, it's got to stay in place more or less forever. Don't assume that once Google has once seen that you intended a 301 that they will remember this. You've got to keep it in place, and if it was a cross-domain redirect, you should plan on holding the old domain in perpetuity.