Several years ago when still involved in a digital recording project to preserve a collection of music previously recorded on cassettes and reel to reel tape I subscribed to ARSClist, which was a project of the Association of Recorded Sound Collections. The list provided a lot of insight usually coming from professional technicians and others with experience in digital recording. This list is aimed at people who preserving archived music, not people recording for resale, however. One thing I discovered is that many business and archives who are concerned about the lifetime of discs use gold CD-Rs. They are more expensive than those commonly used. Cost was around $1.00 when I was buying them. It seems like the brand name was Mitsui MAM-A Gold. Their promotion listed a life span of 300 years.