I know Pam has the Prima Guide. Maybe that info is in there. But, if I had to pull a number out of a hat, I would guess that each tier of fridge quality adds one day of freshness. I'm basing that just on my own experience where food spoils with the 2nd tier fridge in a couple days and stuff stays fresh in the best one for almost a week. But, then you've got the random spoiling bug that throws everything out of whack.