Here's a good explanation on Blu-ray safety
"Blu-ray discs have been available for data storing since 2006, which means that they have not been in use for a very long time. Producers' tests show that optical discs may be used for about 50-200 years. Our experience with older disc formats, CD-Rs and DVD-Rs, shows that well-known brands have invested more into research and development, and their discs are always with better quality.
When using blu-ray discs for data backup, you need to be aware that optical discs may be damaged by direct sunlight, excessive heat and scratches. We suggest keeping blu-ray discs stored in storage boxes, disc cases or in binders (also called wallets). If you need to transport blu-ray discs, use special blu-ray carrying cases."