There is some evidence to suggest that these DVDs have good archival support, and I can guarantee you that DVD readers will still be abundant 10 years from now:
I had about 1000 DVDs in storage of backed up satellite data. At one point I had to restore the backup using the DVDs and it was about ~8 years into the mission so I was worried that the data would be no good on the earliest discs.
It turned out to be totally fine, as far as I could tell. None of the early data had SHA/MD5 sums (I added this later), so there's no guarantee the earlier discs weren't somewhat corrupted, but they were definitely readable.
Back then, I had assumed they wouldn't have that long of a life, but as you seem to have found, and I discovered, once written, optical media seems to have a very long shelf life.
Most Optical Media degrades almost immediately, depending on storage environment, lasting as little as two two years before they start to degrade/aren't readable (depending on the dye and substrate). The MDISC is archival format - designed to last a minimum of 100 years when stored under reasonable conditions, and up to 1000 years if stored in archival (cool, dark) environments.
They are essential carving physical holes into a stone like substrate.
http://www.mdisc.com/