...to whoever was waiting for a Netflix DVD. I had one that I'd been meaning to watch, but because it had subtitles and I have two kids running around with no quiet time to read a movie, didn't get around to it.

Apparently I'd had the DVD for 11 1/2 months! Oops. I just returned it today so hopefully the queue for that movie will go down since it wasn't a famous movie and they probably didn't have many copies.

They store the product digitally and 'burn' a DVD when someone orders it. many placed orders. I think the reason for having a 'return by' system is to keep the intellectual property from escaping copyright control. I knew a guy who had a music CD system and that's how he did it. An order came in and his special printer loaded the digital data on one side and printed the labeling on the other and then off to the postman. He didn't keep hundreds of preloaded discs stored in his garage. He now owns a large ranch in Palm Springs. That's my story and I'm sticking to it. So, don't lay blame on the kids

PS He logged all his production and sent it with a royalties check to the distributors every quarter. All legit.

So what did he do with the discs he got back? And then why do some discs on Netflix say short/long wait?

One, he wasn't renting with the intent to have the material returned. He was selling for the distributors and paid royalties. Oh, wait, I said that already. I only related what I have learned from experience. I will not even attempt to sort out your issues. I could only speculate why Netflix has a short/long wait distinction. But again, I'd say it was due to the demand and wait time to produce a new disc through their limited number of machines.
One failure mode I have encountered with DVDs is a matter called 'greying' of the disc. The laser used to impart oughts and naughts wears out over time. And for a limited time they will only etch tiny values of 0s & 1s. One hit by a reading red or blue laser will erase the data for many points on that disc. The line has to be shut down and a new laser printer/etcher installed. Having failed discs out in the public and making us aware of the downside to disc storage may be why they want them back, too. You read the data too often and the disc goes blankety bloop. So send them back, please. We woill recycle the plastic into new discs. Thank you. Netflix. Only a guess so don't blame the trouble on me.
Offering a general apology was a nice thing and even though I get the same product at the same price buying used on smszon, rather than Netflox, I'm sure some Netfilch customers are grateful/

Some of my DVDs have been replaced due to that failure mode (I don't like paying twice for the same thing). I need to switch to a flash drive storage, Get disc, record to rubidium medium.

Sdd: I call it greying but I think there's another techie term fo it. What happens is that you notice is that the data area goes from a mirror finish to a grey, nonreflective tone.

I get most of my DVDs from the library, so rather than greying, the problem that comes up most often is that it just stops playing entirely, due, I believe, to jam on the disc.

Dead DVDs reveal that photons have equivalent mass and can do work!

And I find that the added mass of a library ID label can damage the spin motor by shifting the disc center of mass (and the pizza cheese does the same thing).