Should Class A Amps be left on??

Sayas: Thanks for the follow-up. Hopefully, your posting of honest findings based on first hand experience will encourage others to check things out for themselves. It is good to see that, even though you initially thought your system sounded quite good, it sounds even better now. As you've found, it sometimes pays to have an open mind and experiment : )

As to the slight fading of dynamics that you are experiencing, i have to wonder if your amp is receiving adequate aiflow. It sounds as if the amp is running TOO hot, which can make them sound dynamically constricted in my experience. How much open space do you have on top of and around the amp ? I know that the Aleph's are all heat-sink, but anything that you can do to let the heat naturally dissipate through convection will only help the matter. Sean
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Sean, the 5 is in a basement on concrete, underpad & carpet and marble slab with nothing surrounding it for 4'. Airflow, cool air is as good as it gets. The listening room is 70F or cooler.
I am confident that the convection factor is as good as I can make it.

Leave them on...most decent Class A amps are designed with this in mind...if you have reservations....and want to turn them off...give them 10-15 minutes of "warm UP" when turning back on...and dont stack other componets on top!
If you have the old MF A1...you can make some chicken fajitas while listening to Mahler..awesome!