Does a brand new electrical circuit for audio gear benefit from burn in/break in time?

Nope: no "burn in" effects.

I'll wager not one of the respondents fully disconnected their system and re-connected prior to the miraculous improvements...

@ghdprentice 

my experience too …. A new 20A line over a 15A line ( both dedicated ) provided a higher degree of slam right off the bat  …this was kinda expected somewhat with more amp headroom maybe, I guess ?

but nada further improvement after that .

While I have been the first to use outlets in a room for my hifi (new house), I have never A/B’d before and after. Saying that, I would doubt that whether it was a space heater or an amplifier, anything would change after 100-200 hours of use.

@ieales 

- not sure why you would even conjecture that … but in any case …nope … that is dead wrong … and you lose that wager …full stop. 

- My entire system was fully disconnected into its individual components and then boxed up and stored away for protection during the house renos

- after full Reno completion six-odd weeks later …THEN …all boxed up components and cables were taken out of storage  and finally reconnected again with new dedicated line and outlets  …. and voila …