If you buy a DVD you have the right, in every sane jurisdiction I'm aware of, to rip the movie from the DVD into an iso. You can then discard/recycle the media and retain the digital copy you have the right to view privately in perpetuity. It is a single consumer license though, as is logical, so it's likely illegal for you to continue to watch the ripped iso if you resell the media with the content still on it or resell the media with any portion of the value coming from the markings from the content or the fact that it used to contain that content. You probably want to shove it in a closet somewhere or just reuse it as rewriteable media for whatever purpose you need - retaining physical ownership of the media makes things simplest legally.

> DVD deteriorates to the point of becoming unreadable

If I am the reason for damaging my purchase then I am fine with that characteristic of the purchase.

Same happens with books, you buy the copy and if you don't take care of it, soon it will become unreadable.