I'm a bit skeptical of manufactures who say that their products need hundreds of hours of break in before performing or sounding good. Although some products do benefit from a break in period (several hours, not hundreds of hours) It has been my experience that good products will sound good and perform well out of the box (so too speak) after being allowed to warm up. I do know that some amps, pre amps DACs and CDPs (old or new and some more than others) will improve in sound after being allowed to warm up before giving a serious listen.
My, tubed pre amp sounds better after about 20 minuets of warm up, but I can't hear much, if any difference, after that. It just sounds really good. I shut it off when I am through listening, to save on my tubes and power bill, if I'm not going to be using it again for several more hours.
My Integrated tube amp sounds best after about 1/2 hour of warm up and I can't hear any difference after that. I also shut it off when I'm not going to be using it for several hours.
My old ADCOM SS power amp sounds best after at least 8 or 10 hours of warm up. When I'm using it in my main system, I leave it on continually. For those with these older ADCOMs, if you're not giving them at least 8 or 10 hours or warm up, you are missing out on how truly good they can sound. Many other SS amps, likewise, sound their best after several hours of warm up....Jim