IMHO those items I've bought brand new worked differently and or better after being used for several weeks or a couple three months. depending on what it was.
If a DAC is simply left powered on, without signal passing thru it, only the daCs power supply is being activated or used.
with a signal as well being sent thru it via X input, to ? output, than that path is being activated. consequently, electricity gets into and thru everything in what ever signal path being used.
for electricity to get from one point to another a completed circuit MUST be in place. here's the issue... if the outputs of X DAC likely analog but possibly digital, connected to say an amp, yet the amp is OFF, I can't see how a completed path for electricity is in place. either the de-energized amp will appear as a 'open cat' or as a 'dead short', more likely as an open or broken path for current, meaning no current will flow thru the analog outputs. likewise if the DAC is feeding a pre/pro digitally and the pre/pro is OFF.
this is why I have, just by chance, a secondary outfit such as a HT receiver that I can burden with these kinds of chores rather than eating up ttubes, or needlessly burning up my main amp.
DACs ought not take more than a few weeks to be up to speed as best as they will ever be.
lastly, I feel running in a thing involves powering it up, and powering it down too.
essentially, its a matter of thermals. heat. heat is what is curing the bits inside. to what ever extent what ever bit needs be heated up and then cooled down.
with speakers it becomes a physical thing as well for the drivers need to be flexed as much as the x overs need juice passed thru it/them.
BTW... there are differing views on this breaking in issue. RWV