Choosing Storage Media
When deciding where to keep your data, remember that everything rots, and everything breaks down. It's the way the universe works, and there's not much we can do to stop it. Therefore, you have to think about your data's lifetime in terms of months, years, or decades.
Very little data most people have truly needs decades of preservation, but often, it doesn't hurt to have it around as long as possible. A minor amount of effort will help mitigate that. Specifically, expect to renew/refresh your data storage every 3 years or so - anything you don't do this with will progressively be subject to bit rot, moisture and heat damage, and being shoved into progressively unpleasant locations at home and office before someone decides it's trash.
Compact Disks, Digital Video Disks, High Definition DVDs, and Blu-ray are all optical media. This means that information stored on them is read by a laser. It is debated how long the shelf lives of these products are, while commonly accepted that DVDs have a shelf of 20 years, and CDs have a shelf life of 3, it is unknown obout the others.
Professionally produced CDs (such as those you would by from a store) are accepted at having a shelf life of up to 7 years. CD-Rs, and CD-RWs, however, have a shelf life of only about 3 years. They store only 700 MB and have only a single layer.
Digital Video Disks
As with CDs, DVDs that are professionally produced have a longer shelf life than recordable ones, although there is less agreement as to how long they last. 4GB on a single layer, double that on a dual layer.
High Definition Digital Video Disks
HD-DVD is dead, having lost the format war to BluRay. It is recommended that you back up any data on an HD-DVD and transfer it to another format.
So named because of the blue laser needed to record and read a Blu-ray disk, Blu-ray is the newest of this group. Able to store 25 GB on a single layer, or 50 GB for a dual layer. The most expensive and restricted of this group as well. Not Recommended. It is unknown how long Blu-ray disks last.