Are you sure they survive for the time period you intend them to? When I was a teenager, I though the DVDs and BluRays I burned would be forever - 15 years later I am very unhappy to find that some of them started to crack and flay - it's a pain to keep checking them. Nothing like the guarantees a NAS + Cloud backup could provide.
sure, but NAS and cloud doesn't fail at the same time. Also NAS provide some redundancy in-house as well. Whereas BluRay is a single copy - even if you burn multiple copies, they degrade at the same rate.
