Optical discs are known for degrading. The chemicals used in optical discs are unstable and therefor the discs become less readable over the years. A French study in which several Blu-ray recordable discs were tested reveals that it makes a lot of difference on which discs you store your valuable data. The archives of France, who conducted the research, tested discs from Sony, Verbatim, Maxell (made by Ritek), JVC and Panasonic.
The discs were burned with Nero and filled for 99%. The researchers used burners from Lite-On, Plextor, Buffalo, LG, Pioneer and Sony, burned them at several speeds and the burned discs were analyzed with a Blu-ray Analyzer from Expert Magnetics which uses a Pioneer drive to read the discs.
An interesting detail is that the researchers make a difference between LTH (low to high) and HTL (high to low) Blu-ray discs. The first are manufactured in a cheaper way and are therefor less expensive. While cheaper, manufacturers claim that the discs are of the same quality as normal HTL discs.
In this test they tested LTH Blu-ray discs from Verbatim and JVC and it seems the claims from the manufacturers are not valid. The tests revealed that the overall quality of Blu-ray LTH discs is worse than normal Blu-ray (HTL) discs. It seems that if you want to store your data for a long time, these should be avoided. The researchers recommend to use normal HTL Blu-ray discs and rated those of Sony and Panasonic as most reliable.
More details, a link to the report and an ongoing discussion with comments from our experts can be found in this forum thread. Thanks go to user robione for reporting it!