I would be fine with having only “completed projects” linked to, to prevent link rot. E.g., LEFTOVERS 2013 / Boomerang still has interesting information about Release “Leftovers2013” by Jeppe Barslund - MusicBrainz even if the campaign ended about 2 years ago.
Also, linking to a “live” crowdfunding campaign would also add economic incentives for manipulating the db, as per my comment in the other STYLE-thread: