Also see: WKRC in Cincinnati, The Wonder Years, Beavis and Butthead

For these the loss of the original music was such an issue they eventually did (or attempted) to re-release with everything as it was. But don't trust things to always be like that. It holds for almost everything: if you want to keep something as-is the best thing is to store your own copy, second best is to rely on an archivist to store a copy but even that's risky.