I always try and use quality media, having got through hundreds of Kodak and Mitsui media. Of the 700 Mitsui SG Ultra II's, around 3% showed a slowdown or had yellow sectors in nero.
Most of the new Mitsui's are 'mame' branded ones and the quality is not as good - even older 'Mitsui''s had a dye change.
The best quality cdr's you can get I would say are the x48 TY ones - Plextor brnaded x48 media is TY. The dye may be Cyanine, but the quoted lifetime of this media when treated well is 100 years - yeah, fine
The car is a harsh environment, but I assume you mean the general temperature and bumps rather than leave the media on the back shelf in the sun - not a good idea for any media. A test I did with Mitsui media in direct sunlight gave 0 errors after 2 weeks which is great. Still, the Mitsui gold spec's only guarantee 600 plays for their quality media - this would seem to indicate no recorded cdr's are meant to last for ages if played continually. Which is why I archive to quality media and watch divx / svcd on the pc and listen to mp3 on the pc or other device all after copying the data to the device or HD.