IMO, at least however long the statute of limitations in that jurisdiction is for things like sexual harassment, physical/sexual assault, etc. Way too many of those types of cases go totally unpunished because there's no camera evidence, and it seems quite reasonable to me to retain that footage so that if an issue arises, the relevant evidence is available. I don't think you should have any reasonable expectation of privacy for committing crimes at work, and while yes that means that there would be a camera overhead recording my every move, I'm not the kind of person that necessarily sees that as a bad thing; that footage would both protect and bind all of us to a clear social contract, and that seems better than just throwing our hands in the air and saying "oopsies, the footage was overwritten! So sorry!"