Archival for the future: optical??

I've held off on building an optical archive of my photos and videos. Given the size of raw video files and the need to "validate" and so on, I'd have to have a staff dedicated to maintining a blu ray library (and a sizable off-site cabinet to hold the disks). Instead, I just download all of my raw files directly from the memory card to two hard drives (one internal and one external), and I periodically back-up to a third drive. My "work-in-progess" files consist entirely of Lightroom catalogues and Premiere Pro projects, and few ancillary documents, which are pretty easy to back up and archive. And my "derived" files are pretty small too--Jpgs and videos for upload. Once in a while, I'll scan in a large-format (4x5) slide, which generates large TIFFs.

I realize that having a non-hard drive third copy would be safer than two or even three hard drives, but blu-ray just doesn't cut it due to size and reliability constraints. Is there any other way to deal with this problem?

Joe