I keep the box because I don't horde shit so every time I upgrade, I sell off my old console as new in the original box like it was just bought from the shop.
Plus in the last decade, I've moved a few times so it's good to have the box to pack it up and move it. The only time I don't keep boxes is when I buy cheaper things like I dunno, a toaster that came in a box etc. The only box I don't keep of something valuable is my TV's because 75 inch and 85 inch TV boxes are way too big to keep around. Although I will keep them for a few weeks or so to make sure I don't have any issues with the TV.
This is the most I've ever talked about boxes in my life and is starting to get a little weird! lol
I kept my Series X box because it’s actually really secure when it comes to moving/bringing it somewhere. Also I bought the extended warranty for it last year.
Nope, the PS5 has just 12 months (voluntary manufacturer's) warranty from Sony. I think what you mean is the legal guarantee where the trader is responsible for 24 months. But even this becomes useless after 6 months, because then you have to prove that it already was faulty when you got it and that's nearly impossible.
I always keep them until I'm sure that I don't want to resell the console or return it, then I cut out the sticker with the serial # and trash the box.
If you ever need to send in for repair, they ship you a box for mailing it in, so no reason to accrue extra clutter.