I use M-disc and I am sure the discs will stay safe for a long time. What I worry about are the drives! It seems the business of making drives is not profitable. So companies exit or reduce.

The author managed to find a decades-old Digi8 camcorder in working order.

M-disc is readable by a standard DVD-ROM/Blu-Ray drive.

The industry has manufactured many, many more DVD-ROM/Blu-Ray drives than it ever made Digi8 camcorders, and they have fewer moving parts.

If you're concerned with finding an M-disc burner, I share the same concern.

If you're concerned with finding an M-disc reader, there's less reason to worry than with any other archival media formats.