I would be curious to know how long a pack is deferrable for?
I no longer have access to the MMEL to give a definitive answer to the question, but everything in the MMEL (Master MEL - published by the airframer - operators can go more conservative than the MMEL, but not more liberal) has been statistically analyzed and approved by the regulators.
My best guess is 3 days, but that's just an educated guess.