[Al Skierkiewicz]

Not to pile on here,
As Mark has pointed out, FET death is frequently metal shavings related but all too often, teams are running inefficient designs that have extreme current demands (i.e. constant or near constant stall on a Chalupa will draw 129 amps). It is these extreme currents that raise the internal temperature that explodes the case of the FET. (Note that the FETs are not mounted to heatsinks.) Going to a higher breakdown voltage FET will do nothing for that type of failure. In general, a single FET failure is shavings related and will usually be accompanied by smoke damage near the base of the FET. A failure of six at a time is temperature related and will usually result in damage to the circuit board.