What's long-term? I have some dvd-rs that push 20-25 years and despite the plastic getting brittle they still work. I also have some ide drives that still work without problems after 40 years. I would rather aim for 20 years and upgrade the storage device if I still need to retain the data.
That's a thought I hadn't had. The plastic of the disk getting so brittle it shatters in the drive due to age. I wonder what's the embrittlement profile of polycarbonate stored in reasonable condition.
Brittleness is not a concern. "Disk rot" is. The dyes used to make writable DVD's were organic (AZO usually), and break down starting at around the 17 year mark (some earlier, if they were poorly made). They have some measure of redundancy built-in, so you may not notice right away. The discs begin to look a bit "cloudy" at first. Eventually they become unreadable.
Go with inorganic blu ray media if you want longevity. Most HTL blu rays made currently will last around 100 years if properly stored. If you need longer there are M-Disc's, but they are expensive and rumor has it that ALL verbatim 100Gb blu rays are essentially M-Discs with different labels these days.
For all practical purposes any Blu ray larger than 25Gb is probably inorganic HTL, but if you worry a lot you can buy more expensive "archival grade" discs from Japan as well that have been vettted and tested.
I've personally never noticed brittleness in old optical discs (unlike the polystyrene jewel cases, which often turn brittle). I don't think shattering is likely, but if it's a concern some optical drives allow limiting the maximum spin speed. If the drive supports it you can temporarily set it with the -x option of the "eject" command from util-linux.