Just to add some more anecdotal evidence for optical: my group stored satellite data on DVD-Rs, starting in 2003, and in 2012 the earliest discs were still read

Just to add some more anecdotal evidence for optical: my group stored satellite data on DVD-Rs, starting in 2003, and in 2012 the earliest discs were still readable. Luckily, we had several forms of back up of the data, so the loss of the DVD-Rs wouldn't have affected us.