100GB M-disc media and writer

I’ve taken delivery of a M-disc Blu-ray writer and some 100GB BD-XL discs, fresh from Japan. The interest is that the latest Blu-ray discs have 100GB or 125 GB capacity, which is quite useful for photo storage, especially so if you wish to archive digital negative files, which are much larger than .jpg or .png files commonly used for finished photographs.
M-discs are supposed to be the best for archival, much better archival stability than ordinary writeable DVD or Blu-ray discs. Storage estimates are based on accelerated ageing tests in extreme conditions, these suggest that, once finalised, M-discs have an estimated archival life of up to a thousand years.

I’ve had some issues with getting software to work with my hardware combination but I’m confident I’ll get there eventually.
The other way to do this is to make two copies of the archive disc using conventional recordable media, store them separately and check every few years that all is well. If there’s any sign of degradation, difficulty in reading or fragility of the disc, then I make a copy at the first possible moment. Most of my recordable CDs, made in the mid 1990’s are fine but one or two the disc has become brittle. However it has been possible so far to make a 1:1 copy of all suspect discs.