Didnt go this time, but they are normally picked through an hour after the sale starts
Not sure on them restocking, but I went yesterday and it was pretty cleared out even an hour and a half after opening (about 45mins in line to get in). If you were going to go, I'd say be there before opening. Prices were pretty good, 55 hoodies, 250-300 jackets, don't remember anything else though sorry.
it depends on what you're buying. they frequently have 40-50% off sale. even 75% a few months ago IIRC. stuff is usually average but you're not going to get any big name brands such as alden or nanamica which almost never go on sale so 25% would be pretty awesome.
a lot of the "in good company" brands don't qualify for the sale. then again, i've had it work on some so it's a tad hit or miss