I'm going to go out on a limb and recommend an external hard drive. It's fast, reliable and if only powered up when backing up and restoring, it should last as long as your next three computers.
DVD/RW is not a long term storage medium. The dyes used are not stable and recordings will degrade over time. Eventually there will be an error and then the entire disk may become unusable. Depending on storage temperature and quality of manufacturing, it may last only a year. Less if you leave it in a car on a sunny day. Keeping them in a dark and cool (not frozen) place and they may last ten years.
Archival storage of digital content is a major headache. So much data and so many ways it can get corrupted; temperatire, oxidation, cosmic rays, natural background radiation, etc. No single media has emerged that provides reliable long term (100 year) storage. Currently, archives are being stored in duplicate then getting re-duplicated ever few years onto new media. Takes a lot of time and money, but the libraries think it's worth it.
Fav quote - "Experience is whatcha don't get 'till ya don't need it no more."
System - Athlon 1.4GHz, Win98, Hauppauge PVR250 receiver and compressor.
Software -Magix Movie Edit Pro 10, Nero 6 + NeroVision Express, Moho 4.61, PSP 8.1, Bryce, Quicktime 6.52 pro, Goldwave 5, DVD-Lab.
Cameras - Panasonic GS9, Canon ES8400V, Canon EOS D20 and Canon A70