Not optical disks, which are commonly used for selling such stuff. If you preserve your archives using them, you are in for a nasty surprise. And who sells games on hard drives? So the way it works - you buy digitally, and do a proper back up of your copy using whatever good storage you want. Not optical disks though.

Surely longer than DRM.

That's why don't buy it with DRM naturally. You need DRM-free games to preserve them long term. Or otherwise, you'd need to break DRM to do it.