It certainly wouldn't hurt to run a regulator with a LiFe pack. I personally don't. I have used a LiFe pack while using 3121's, 3421's, and 341's, and I haven't seen an issue yet. All my new planes for the past year I only run the 3711 high voltage servos, and no failure.

So if it makes you nervous to apply more than 6V's to what ever servos you use.. add the regulator and be safe.

Randy