To the OP, don't be concerned about having the amplifier on while nothing is being fed to the amplifier. The speakers are taking minimal wattage when no signal is fed to the amp. The power consumption should be low, maybe less than 50 watts, in idle. No damage will be done to the speakers or amp if they are left on.
To clarify, I am refering the amplifier power being on full-time, not the bi-amp bridge on the Axioms, as Mtryoda said.
I had to say that for liability reasons.