First Officer reported a generator drive failed after take off. The flight crew returned to departure airport after conducting a fuel dump.

Narrative

Flight was delayed for departure due to left center fuel pump running during the ground test post fueling. Pressure light did not come on as it should. MEL applied. Inbound flight had a RGEN fail. Mechanic stated they had replaced several parts to no avail. He found it to be over serviced and corrected it. A ten minute engine run followed; and discrepancy was written off. Shortly after takeoff from [Runway] XXR; RGEN fail and associated STBY BUSS FAIL EICAS appeared; coupled with RGEN disconnect on overhead panel. Ran the checklist. Reset unsuccessful. APU restored STBY busses. We leveled at 23;000 feet; talked to the Flight Attendants and initiated a SATCOM conversation with Dispatch and Maintenance Control. All agreed; given the chronic nature of the RGEN problem and the prospect of night ETOPS; the correct decision was to prioritize safety and return to ZZZ. We all agreed to dump approximately 7;000 pounds of fuel from the center tank and then we returned for an uneventful overweight landing (91;000 pounds). I would like to see some clarification on the merits of dumping fuel. Elements of the flight training department are teaching that dumping fuel should only be accomplished if necessary to prevent CFIT. If this is an official policy; I would like to see it in writing. If not; perhaps it is worth discussing further in some medium. There are risks involved in a heavyweight landing; and also with dumping fuel. Further guidance would be helpful.