We all have our views and opinions, including technicians and engineers. Depending on the design of the product on/off can play a role for one and a different role for another. I have tube gear for phono stage and preamp, SS for power amp. Everything is connected to a quality AC conditioner with surge protection. I turn on about 30 minutes prior to listening and turn off when done. Heat is the enemy of electronics and my preference is to minimize heat exposure to my electronics. Tubes have a life span far less than SS gear so it's a no-brainer to turn off that gear after use. For simplicity sake, the SS amp is turned off as well.
That said, even with the 30 minute warm up prior to listening, there is ALWAYS a period of running time in which SQ gets better. I find that about 30 minutes in of listening and the imaging improves, bass gets tighter, and soundstage gets wider. About 45 to 60 minutes and all improves still again. Listening and enjoying the slow improvements is actually rather fun. Personally, I prefer to do things this way rather than have heat prematurely deteriorate the electronics. As stated, we all have our views and opinions; these are mine, yours may differ.
That said, even with the 30 minute warm up prior to listening, there is ALWAYS a period of running time in which SQ gets better. I find that about 30 minutes in of listening and the imaging improves, bass gets tighter, and soundstage gets wider. About 45 to 60 minutes and all improves still again. Listening and enjoying the slow improvements is actually rather fun. Personally, I prefer to do things this way rather than have heat prematurely deteriorate the electronics. As stated, we all have our views and opinions; these are mine, yours may differ.