Thanks for the additional feedback. In Southern California, if you are near beach (like I am), the temperature is seldom really hot and the periods of high humidity don't align with the periods of high heat. Nor is smog a major issue. The only environmental problem, I am aware of is salty air, especially in the winter and June.

Don't know what others' experiences are like, but I have only had two power amps in over 40 years. A Quatre that failed with a cracked board after over 20 years of use and its replacement the Parasound HCA-1200IIA. Perhaps I am being naive but I was rather expecting both the Parasound and the 750 to last for at least 10 more years.