Leaving your hifi powered on

My personal experience for what it is worth:

I always turn of my hifi & TV when I am not using it (even for twenty minutes). My Arcam Delta was my main amp for over 15 years and still gets used a few times a week in my gym system. It has been completely reliable. My first Hitachi TV was 13 years old and still working when I passed it on. My second Hitachi TV was 7 years old and still working when I passed it on.  My Onkyo 875 is a few years old and no problems so far. The only hifi component that has broken on me was a pioneer CD player and it was a few years old.

I will admit that I think my system sounds better after it has warmed up but I do not know if it is:

a. The hifi

b. My ears

c. Placebo effect based on years of reading hifi mags.