YouTube is a private entity; as long as they comply with the DMCA, they're under no obligation to take content down or even make content available (outside of contracts they enter into voluntarily). The DMCA doesn't provide strict timelines (just that the initial takedown requires the provider to "act expeditiously", and nothing for restoration).

The bigger issue is that Content ID has always been a way for YouTube to side-step the DMCA in a way that's beneficial to big copyright holders -- channel operators assume risk fighting a takedown in a way that was never a part of the DMCA.