I didn't want to be alarmist, but I would agree that 5 years is a worst-case lifetime.
There is an order of magnitude difference in lifetime between the metal pressings in commercially produced discs and blanks for home use, and the higher the data density the lower the lifetime, as a general rule of thumb. Also, write-once are generally longer-lasting than re-writeable, due to the stability of the dye used.
So WORM CD-R blanks will last longest, with RW DVDs lasting the shortest time.
And of course, manufacturing quality needs to be considered, with some poor-quality media being little better than junk. But then most expensive doesn't always equate to best performance either.
The Dastard digital photo collection is stored on disk, backed up to disk (twice, once to another PC and also to external HDD) and then archived onto CD-R, as being the media with the best storage life (I hope).
SD