I take these claims with a grain of salt as DVD's have only been around for 13 years, and the current formulation have only been around for a couple of years. I've been involved in enough "simulations" to be cautious. If "forever" turned out to be 5-10 years, I'm concerned about what 100 years might turn out to be.

As mentioned above, I agree that TY media, non-printable, is the best out there today. I mark them only on the internal plastic ring, not on the back opposite the burned surface. I'll probably re-burn them every 5-10 years, although I suspect that copying to new formats may be faster than that. I'll probably be able to transfer to archival grade Blu-ray in 2-3 years.