Some countries even explicitly allow you to break DRM to make a backup copy of your physical media.

To pick one country, Germany for example: There it’s called the “right to make a security copy”. Paragraph 69d (nice) of the copyright law states:

The creation of a backup copy by a person authorised to use the programme may not be prohibited by contract if it is necessary to ensure future use.

That means physical copies have, legally speaking, an endless shelf life.