I'm curious what the legal requirements for this will be. But I imagine they'd want to hold on to data of driving scenarios for at least a month, in case they get accused of wrongdoing by other drivers. If they had no data to back up their case with all those sensors, it would look awfully suspicious and essentially one witness against nobody - so they'd have to hold onto the data for however long the legal teams deem is okay.

This may sound crazy, but it's already happening at the scale of testing with just a few dozen cars.

https://arstechnica.com/cars/2018/06/gm-settles-with-motorcy...