I would imagine that running the Class A-biased Lamm amp on a 24/7 basis would add an extra $50-$75/month to your electric bill - being Class A-biased, it's probably pulling 700-800 watts at all times. Another potential issue is maintaining bias, as some solid-state Class A-biased amps have to be periodically re-biased due to bias drift, and running them constantly may pose a maintenance issue. Don't get me wrong - I really respect the Lamm Class A-biased amp, but such designs could be more practical. I have owned a Class A-biased triode tube amp for ten years (VAC Renaissance 70/70 and 140/140 monoblocks), and can say that they get hot and use a shitload of electricity.
Not to stray off topic, but it could be that you burned through tubes in your ARC Ref 3 preamp precisely because you turned it off and on instead of just leaving it powered up 24/7. Contrary to popular belief, gear that uses small-signal tubes often experiences much better tube life if left on continuously as opposed to turning it on and off. The question I would have about the Ref 3 is whether the 6550 in the power supply would hold up if the preamp was left on continuously. Tubes in preamp power supplies sometimes pass a fair amount of current, and like output tubes in a tube amp, will last longer if the unit is turned on and off.
Not to stray off topic, but it could be that you burned through tubes in your ARC Ref 3 preamp precisely because you turned it off and on instead of just leaving it powered up 24/7. Contrary to popular belief, gear that uses small-signal tubes often experiences much better tube life if left on continuously as opposed to turning it on and off. The question I would have about the Ref 3 is whether the 6550 in the power supply would hold up if the preamp was left on continuously. Tubes in preamp power supplies sometimes pass a fair amount of current, and like output tubes in a tube amp, will last longer if the unit is turned on and off.