How long does a DAC take to burn in?

Over the years I've had all sorts of pieces of equipment where no break in was specified by the manufacturer.
But my personal experience is that most things DO seem to improve over a few hundred hours of use.  I'm not sure about things like cabling, but certainly electronic components and speakers (IMHO) do tend to improve with age.

My Ayre Codex DAC took about 400-500 hours to breakin.  I'm probably at 800-900 hours now and they sound fantastic at his point. Very happy with the sound. 

100 hours ! Industry unspoken standard! No true set time! I call it " till it pops " Reproduction seperates and stages! I.e.: life like sound!

I think only speaker drivers open up or burn in...the rest is probably you getting used to the sound.

Nitewulf has very good point and is probably on the right track in my experience.  The mind is very powerful and automatically starts filling in gaps and frequency observations while listening to familiar music.