I've searched around in the Product Documentation and the Discussion's here, and most references to URL's expiring relate to Smart List Subscriptions (changed via the Admin panel), and Report subscription links.
I can't find out what the default expiration of Marketing Email links are. I'm trying to find out whether an email from six months ago could re-activate a CTA, which leads to a Smart List trigger that may not have been turned off.
I can't find out what the default expiration of Marketing Email links are.
There's no expiration, period.