For every track in your playlists: the version closest to the original recording, the most played, the live ones. With every new hi-res release: an e-mail, one click, your playlist is up to date. The audit covers Qobuz, TIDAL and Apple Music; Spotify and Deezer sync to those platforms from an exported file (their catalogues stop at CD quality, nothing to audit there).
One credit = one audited track, usable for 1 month after purchase. For one big playlist, once. New versions keep coming out after your audit — with the plan, an e-mail tells you and your playlist is updated in one click.