I don't understand why you think you're better than the people buying stuff, when you are also there, looking for stuff to buy?
At least it wasn't boxing day this year, the day after instead- that's something positive for the staff.
I worked for Next for a good few years, there's always a lot of bullshit about the sale.
They pull all the years old stuff out the back- no. Stuff is almost always in for one season, then reduced in the sale. 85-90% of what is on the shop floor in December will be marked down. The remaining bit that's not out will be transitional stock, until they get more spring summer in, and will be marked down in the March mid season sale.
Stock that is in the stockroom now will have been on the shop floor any time from mid July onwards, and will also be reduced down and come out.
Any stock that is not sold in about the next week or two, will be shipped out to clearance stores at that point. It isn't kept in store. There might be literally the odd few bits that were found mixed in a rail or something, but only a handful and they tend to get marked down automatically to a lower price on the till, so they'll be dirty cheap.
They send all the stuff from the clearance stores to the shop- no. The clearance shops have they're own ranges as well as ex-shop stock, it's different labels, it doesn't go to the shops.
I don't know why it's so busy- because when a lot of stores have historically started their sales at 20% off, next have always, for their own brand stuff, gone in at 50%. They want a quick turnaround. It works. It goes quick.
There's no good stuff left- very true. It goes quickly. The staff get the first pick (at least when I was working there). It's the week after Christmas when they've just worked their arses off until 6pm on Christmas eve, after a shit December, and had a single day off. They deserve their perfume set at half price. We also used to have friends and family work just Christmas eve, to set up sale, and they could stick a bag of stuff away too if they wanted- we had some who did it every year for the early access. Don't know if they still do this.
Then you get the people who KNOW that they want a lot, so they get there at 5, they pick everything up in kids size 12-18 or whatever, then go take it into a corner and pick through. Or just buy it and return.
It is messy, and it's shit for the staff. You just have fitting rooms full of stuff that's been dumped/ fallen on the floor, and you just have to scoop it up, dump it in there, and have a member of staff processing as fast as they can all day long.
Next has now changed it's return policy to 7 days for sale stock to be returned, so try checking this time next week instead- everything gets processed as it's returned and back out so some good stuff comes back.
Resellers- probably are there buying, but as they've only got 7 days to return it, they either take the risk at keeping it and holding it til next winter, or it's back in the store next weekend. I don't see the problem with reselling, it's a way to make a living.