http://www.mdisc.com/what-is-mdisc/ for those curious - it appears to be a stronger archival DVD/blu-ray that is already burn-able on certain drives that are on the market.
Has anybody used these? A 1,000-year DVD/Blu-Ray sounds good. I would use it if it is actually reliable. (Actually just want decades, but centuries is better.)
Non LTH BD-R has an estimated lifetime of 50 years if stored properly. 40 cents a disk. In a cd case, in your closet.