I used to work at an Apple retail store, and I'm pretty sure we didn't have turnover every 5 days. Of course this is an average, and I'm not exactly sure what it's measuring, and regardless we definitely got a lot of stuff shipped every day.
From what I hear of my wife's job, though, it sounds like Trader Joe's turns over its inventory every 1-2 days.
You make a good point, and while I don't know the answer, maybe online sales play a part in their turnover rates? And it's possible that some large stores (think NYC) have 2-3 day turnovers, with others being slower?
Like I said, I don't know, but those are two variables I can think of.
From what I hear of my wife's job, though, it sounds like Trader Joe's turns over its inventory every 1-2 days.