In my company the FDR and CVR are not reset by the flight deck. At the end of recording period the units simply start recording over the first data recorded so there is a rolling log of the preceding period. The engineers can erase the CVR units using a switch on the outside of the aircraft if required
Additionally there is a QAR which automatically uploads data to the company's Flight Safety department where it is checked against a set of predetermined limitations. This list is pretty comprehensive and covers such things as 'gates' on the approach eg fully configured by a certain point on the approach. This is used to assess trends within the fleet.