heat

Don't cover when in use. +3 for air purifier, I don't run it while listening. I just installed one for the entire house.

All electronics fail first due to mechanical fatigue. This can be caused by several things, vibration, hot and cold thermal cycling and intermetallic formation.

Even if you don't listen loud, the pre-driver and driver transistors are biased high enough to produce significant heat. This heat will continue to build over time during your listening period without sufficient ventilation. The heat sink design for these transistors, most likely NOT mounted on the output transistor heat sinks, will cause ALL components to get quite hot thus lowering their life expectancy.

Well, he only listens about once a week and this is a 600+ watt/channel Mac. It is very well designed and can take the on/off without a problem. My SS amps have been switched on/off for 42 years and I haven't had a problem, knock on wood. His McIntosh kills my amps!