I bought last time DVDs in August of 2007 and CDs way earlier. They still work whenever I need one (and I'll probably never get to use them all). Write, verify, move along.
I've burnt to 10+ year old disks and they still work fine, mine are probably medium quailty disks but they are white printable ones and on a spindle so no idea what brand they are. DVD's do degrade over time but I think Taiyo Yuden were supposed to be really good quality ones weren't they?