Initial warm up/break in, out of the box, did seem to be a more protracted process.  (Maybe cap burn in is a part of this?)  A few weeks back, our power was turned off for a day because Edison was replacing a damaged pole at the end of the block.  My yggy seemed to take a day or two to come back up to speed but not a week + like the initial turn on. 

Just make your Yggys more cat friendly:

I have come to understand this subject as a matter of acclimation.

Each component part used in any new piece of gear has never been in a circuit before.  Indeed it has never been exposed to voltages and current and frequencies and heat etc., other than what it was subjected to during manufacturing and subsequent assembly and testing.

These aren't the same conditions under which we listen to music thru these devices.


And these active and passive components function within quite specific parameters where they will remain for the rest of their operational lives. 
And as the hours accumulate they will 'settle into' their environment and accilmate to those parameters.   
I see this as a 'formula' for 'break-in'.

This 'explains', at least to me, why there is break-in in the first place and why the device will take less and less time as the total operational hours continue to increase, to reach its peak operating condition after a shut down. 

And a related term I use is 'thermal cycle' which describes how it can take several cycles of reaching full operating temperature and then cooling down to ambient, for a change made to a complex system to re-stabilize for the full effect of the change to stable and become 'known' and repeatable.

These are similar patterns to those I have noticed in many different types of machines, both mechanical and electronic.

JJ