I don't think they should be keeping data that's not involved in an active warrant.

However, if they do anyway, there should be strong victims' rights protections so that the data is actually used during investigations.

There was a string of burglaries in our area a few years ago, and panopticon N-1 (Google Map's auto recording of all phone GPS traces for marketing information) could have found the perpetrators pretty much instantly.

They hit rural outbuildings in the middle of the night on camera, so timestamps were precise, but faces were obscured. A reverse geofence warrant keyed on time of arrival / departure would have narrowed it down to just the crooks with extremely high probability, and other details in the videos would have corroborated the GPS traces.

None of the victims were politically connected, so the police couldn't (by policy) run the reverse GPS lookups. This is the worst of both worlds: Our data is recorded to be used against us later, but if ever it would be useful, we do not have access to it. The same is true for vehicle black boxes / cameras. They record a few seconds before airbag deploy, but you usually are not allowed to access them as part of an insurance dispute (even the ones from your own car).