[betterth]

"so they can't be sold and will stop working at some point, most likely within 5-10 years."

This is incorrect, it would be more correct to say that they could stop working at some point.

It's entirely possible (and has been done before) for the company to patch out the DRM before turning servers off or going defunct.

The internet is also full of no-cd cracks that generally circumvent this kind of always-on protection (at the expense of breaking multiplayer) without circumventing serial code or other protections.