I recently bought a Panasonic PV-GS19 (which I love) and have been making a lot of movies starring my family and my new wife. As you can imagine I'd like these movies to last for years, so I've been burning them to DVD. How long should they stay good? Apparently it's a matter of technology and quality. As with other products, DVD manufacturers mass-produce a huge number of units, many of which come off the assembly line with defects. The near-perfect units are sold under expensive brand names, and the slightly defective units are sold more cheaply through side companies. A knowledgable friend recommended Taiyo Yuden DVD-R discs to me through SuperMediaStore, and I haven't had any problems with them yet... but it's only been a couple of months.
Update 060117:
Reader John V. passes on this additional article about recordable media quality.
