I guess you need to decide why you're putting the fish in quarantine.
If you're worried about the fish developing ich, then 2 weeks is a minimum, IMO, especially at temps below 75.
Look at the major diseases that a fish can introduce. Many of them won't show symptoms until after 2 weeks. Many won't show symptoms at all, they'll just spread it to your other fish. The purpose of a q-tank, IMO, is to prevent the entire tank from catching the problem, and to introduce the new fish to my water, my maintenance, my feeding, etc. 2 weeks is barely enough time for health clearance, much less anything else.
FWIW, commercial hatcheries that have disease issues aren't considered clean until they've tested clean for 12 consecutive MONTHS. Of course, a lot more is riding on healthy stock there, but it's a thought.