The concern is not a one-time conversion to MP3 but several generations of MP3s derived from each other, each one with more artifacts than the last. It's the sa

The concern is not a one-time conversion to MP3 but several generations of MP3s derived from each other, each one with more artifacts than the last. It's the same problem we experience with image compression. Lossy compression of a lossy source results in a lossier output. From a preservation point-of-view, it's best to have a lossless (perhaps compressed) copy and use that as a source for whatever arbitrary audio format we're using decades from now.