Compact discs might not be considered new technology these days, but when they were first released they were marketed as practically indestructible. Compared to the two other audio storage mediums of the time - cassette tape and vinyl - that certainly seemed to be a easy claim to make. CDs later became a popular storage medium for video games as well, thanks to their low cost and large capacity.

Back in the mid-'90s, Nintendo caused quite a stir when it decided against using CDs on its Nintendo 64 system and stuck with expensive and (in comparison) lower-capacity cartridges; its two big rivals, the Sony PlayStation and Sega Saturn, both used CDs. Nintendo's choice cost it dearly, with many of its previously loyal third-party supporters ignoring the N64 in favour of the PlayStation, but from a retro collector's perspective we should perhaps be thankful that Nintendo was so stubborn - because there's now overwhelmingly compelling evidence which suggests optical media isn't quite as robust as we've been led to believe all these years.

An excellent feature on the phenomenon of "disc rot" has recently been published on Tedium, and is well worth a read. We'll attempt to summarise here, but the long of short of it is that CDs - and most other forms of optical media - have much shorter lifespans than previously assumed.

When CDs were first released it was estimated that they would last a lifetime - some brands even claimed over 100 years of service - but in recent years many collectors have begun to discover that CDs that are less than 30 years old are now useless.

So what is disc rot? Well, for starters, it's not really "rot" - what's happening is that the chemicals used in the disc's protective layers have failed over time. Another cause is the oxidation of the disc's reflective layer, usually made of aluminum. In some cases, the discs begins to "bronze" over; in others, small dots appear which grow in size as the layers inside the disc break down. As you can imagine, disc rot presents a massive problem not only for collectors, but for those people whose job it is to archive important or historical data; many institutions use CDs and DVDs for storing large amounts of information, and the terrifying reality is that these discs could become unreadable in quite a short space of time.

We'll let blogger "slackur" (also known as "Jesse Mysterious") explain this harrowing phenomenon in relation to video games - they wrote this post back in 2010:

Even though it is only one little dot, it represents damage that cannot be repaired. No scratch removal process can restore the data that is now lost. The game is forever damaged, and likely to get worse over the years.

Now, many sources online will claim that disc rot is a limited-scope problem, concerning only a few years worth of discs from certain manufacturers, (and CD-Rs) and that it is not wide-spread.

But when I learned about this problem, I checked my several hundred discs between Sega CD, Turbo CD, Saturn, and even Dreamcast games and found DOZENS had this problem. Several expensive games I owned were mint—except when held to the light I could see one or more little white dots that proved my game had damage. Some of these I went back to play after not touching for years and found they now would occasionally lock up or not play at all. I had a few FACTORY SEALED games that I opened and found the same thing.

It has been a nerve-shattering nightmare for a collector like me.

From a gaming perspective, slackur's blog post above sums it up quite neatly. While music CDs and DVDs vary in value, no entertainment sector has quite the same inflated prices as the world of video games. Certain titles fall out of print and end up being worth hundreds - if not thousands - of dollars on the secondary market, and the thought of those games becoming totally unplayable over time is sure to send many a collector into a spin; some may already be losing a fortune as we speak.

Which brings us back to the N64. Cartridges are traditionally quite robust - hence the fact that people are still happily playing Atari VCS and NES games on original hardware - so N64 games should continue to be playable for quite some time yet. However, if slackur's observations are correct - and let's not forget those comments about Dreamcast games suffering from disc rot were written seven years ago - then that super-expensive copy of Panzer Dragoon Saga you have sitting proudly on your shelf could well be coming up to its expiry date, if it hasn't reached it already. This situation also reinforces the need for video game preservation and - for once - gives a solid argument for emulation. Without it, we could stand to lose many video games for which the original code no longer exists; the aforementioned Panzer Dragoon Saga is apparently one such title.

So when you go to bed tonight, remember to give your N64 collection a little cuddle and thank Nintendo for digging its heels in back in the '90s.