Longevity of DVD-R and CD-R / 2-Media Hedge

I've had long discussions with an archival specialist here in Denmark on the topic of what media to use for what purpose. The unanimous result was, that "archival copying" is a never ending job. One can always quarrel about the life of a media, but in practice this is a fight about the emperors beard : it is useles. The fact is, that the development of drives is so quick, that even if you _could_ save a tape or disk or CD or whatever for 30 years, you wouldnt find the proper drive, and even if you did, it wouldnt be supported anymore. Let's go back 30 years; what were the dominant media at that time ? 1600 bpi reel-to-reel tapes, 7.25 or 30 MB harddisk (IBM 2311/2314), and 8" floppy discs. Some of my customers _still_ accept 8" disks and reels for financial transactions. In my experience, the conclusion is that the more "modern" the media, the shorter the life span, e.g. 5.25" floppies : probably late 70's to mid 90'. Especially streamer tapes are a problem; some drives are only 1 generation backward compatible for writing, and maybe 3 or 4 for reading. As the capacity doubles more or less each year, the horror scenario is that you cannot read your own tapes after 3-4 years because of drive incompatibility. Nico