The DAC no longer locks on to 24/192 files through Toslink any more: I got lots of clickety clicks from the internal relay when I started listening to 24/192 files this evening and after a couple of hours or so, couldn't get a lock on any 24/192 files. So I guess the DAC does indeed "burns in" to approaches its intended speck.
However, now the sound from 24/96 files is becoming something special, especially
these files which through headphone listening (Earmax pro headphone amp and Sennheiser HD650) are the best and most musical noises I've heard through my headphone rig ever. At the weekend (during the day when I'm not going to annoy my neighbours) I look forward to listening to these files through my speaker-based system.
All I can say is well done CIAudio, I still have issues with the VAC-1 which may or may not be cleared up. However, the quality of the DAC is obvious and if I end just using the stock power supply with a step-down transformer so be it.