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.