Streamer always on?

The reason I ask is that it seems to be sounding better after a couple of days.

Break in always helps, as you already noticed, especially if there’s an internal DAC 

FWIW, A wise, very experienced electrical engineer once told me that all electronic gear is designed to run hot. Going from hot to cold & back again is the greatest stress on the gear. Then there's the cost of the electric bill to consider.

Temperature cycling is a common method for testing component reliability and life testing. Most if not all discrete electrical components last longer when temperature cycling is minimized or avoided altogether. 

I remember reading an article many years ago about this subject. The biggest concern this article said was with transistors, after thousands of cycles of turn on and off, (heating up, cooling down) the body of the transistor would start to develop microscopic cracks, which would cause it to eventually fail. I have no proof of this as all I can go by is what I read in this article. YMMV.