If you have a fully ballraced servo, of more than standard torque (I'm actually running a mere Hitec 325HB single bearing 51oz servo), then having a TRS set up to close a dead servo at WOT works fine. Yes the servo has to work harder, but it hasn't slowed it down any (which I'm suprised at). And the battery depletion concern is really pretty inconsequential, that's like not upgrading to a more powerful steering servo because of battery life concerns.

I've never had a battery go flat whilst out bashing in any car (three in total) with a TRS set up to close the dead servo. Guess it depends how long you bash for.