I still have a bunch of 148's in the "old servo" box. True, likely not much will happen to them, but...they were/are Futaba's lowest end servos. While I too ran 5 cell NiCad packs with them, note that 4 cell NiCads can produce up to 5.8v right off of charge. Five can go to 7.25. LiFe's can be 7.3. So while rated for "6v", they get pushed to up to 50% higher than the nominal 4.8v they were originally designed for. This is, of course, only for perhaps the first flight or so, and then the packs settle down to their rated voltage. I have seen premature death due to higher voltages back in the 5 cell days, but it was pretty rare. The biggest issue with those servos was that they used the hole in the case top as a bearing. The hole would elongate due to wear over time, and the servos would get worse and worse at holding neutral as the shafts rocked back and forth under load. I may still have a few that were retrofitted with aftermarket ball bearing case tops....but that didn't really improve them all that much. Best use would be for throttle only.