My DX7 does not need to have the power switch turned on. It just turns itself on in trainer mode (i.e. no RF transmission) when you plug a trainer/sim cord into the trainer port. I believe the Futaba transmitters work the same way. So even though the transmitter batteries last a lot longer because no radio transmission is occurring, the batteries will still eventually wear down, and you need to remember to unplug the trainer cord from your transmitter when you're done playing. The nice thing about the dedicated sim controllers like the RealFlight one are that they're powered off the USB port. Personally I'd rather use my real transmitter anyway though, because the sim controllers just feel too different from my transmitter. Others feel differently though and like the idea of not wearing out their expensive transmitter while practicing on the sim.