An idling, but "ON" power amp will not heat your voice coils. It has no output. Music signals WILL heat your voice coils and heat WILL cause them to expand. If you don't want your voice coils to expand, don't use them! However, since they're designed to operate with heat (up to a point) heat won't damage them at all. Leaving your amps on will not help or hurt your speakers. Electrical devices are all somewhat like light bulbs; leaving them on all the time results in the max. total operational hours (everything has a limit). Flipping them on and off rapidly results in early failure from heat cycling. Turning them on for use and off when not needed gives the greatest calender life. You choose what is most important.
Leaving Amps on
I am wondering, in the case of which is best for the speaker, is it best to leave the amps on all the time, or shut them off between use. I know that turning them on and off causes heat expansion in voice coils leading to stretching; The main reason that pro audio setups that are permanent stay powered up all the time. But, is it really best? Can I also cause long term damage to the speaker by leaving it powered up with no signal being sent? I just recently read an article that said too much continuous power can burn the parts in the coil. Can anyone help? Thanks in Advanced! Sam