I have a Rel B3 and never turn it off. It goes into standby if it doesn't get a signal in 20 min and then uses only about 7 watts. A warning in the manual says if you do turn it off wait 20 min to discharge the power supply or risk damage to it. My way around that warning is to turn it off while playing music (I hear the sub still playing for about 30 seconds).
That being said other manufacturers may be different.
That being said other manufacturers may be different.