Though it may sound like a wonderful idea, Snopes Says The LOC ain't converting over to 78 any time soon.
Another interesting bit about how things last — the Library of Congress completed a study on the best medium for near-permanent archiving of their extensive audio collection. Their conclusion — 78 RPM platters. Unlike in my dad's day, the medium (platter) itself can be made to last nearly forever with today's technology, and the recording can be reproduced with a very simple mechanical device and no electricity. This came up because of concerns that rapidly changing technology (LPs, cassettes, 8-tracks, CDs, DVDs, flash-drives, DVRs, whatever's next) made it difficult to ensure that older archives could be retrieved. It was my understanding that they have already begun transferring audio recordings from various media to 78s.