Our eldest daughter asked if she could have some music on the other evening - and following a quick finger through the first few CDs in our rack, I pulled down ABBA Gold (she went to see Mamma Mia recently, and has been humming the various tunes ever since).
Our copy of ABBA Gold was bought when it was first released - 1992. That makes the CD 16 years old. It is in (outwardly) perfect condition, and has always been stored out of sunlight. It no longer works.
After checking a selection of other CDs from my days of disposable income, I discovered that some do still play, but a worrying number do not - perhaps a quarter of all CDs over 10 years old are failing. I knew recordable CDs and DVDs have a horrendously short lifespan, but had never really thought about commercially produced CDs.
Just to horrify you, I did a search of the internet and came up with the lifespan of most CD-R and DVD-R discs as being anywhere from 1 to 30 years, dependent on the quality of the media used. Most people buy the cheapest media available, and the 30 year figure is almost certainly a marketing term - where the discs were theorised to be stored in a dark vacuum, or some other such unfeasible situation.
Finding anticipated lifespan of commercially produced CDs and DVDs seems to be much more difficult. It would appear that CDs and DVDs are susceptible to commonly occuring bacteria, and to oxidization - which certainly explains why some of my collection is failing.
The situation is made even more murky because CD players were designed to survive errors. The data format used allows for huge swathes of data to be “repaired” by some very clever algorithms - this is essential due to the nature of optical media (you try aiming a laser at a track of bumps a couple of microns wide). The upshot of this is you don’t know your CDs are starting to degrade until it is too late.
Perhaps keeping music and movies digitally, and replacing mass storage devices every few years is a good idea after all?