DAC break-in...

As in all things Audio, it will be system dependent. Several variables will make it impossible to determine the break in length in your system. I will list a few;.... system resolution, your listening acuity, quality of source material and associated equipment.

Once you get the DAC installed I suggest you let it settle in by running a signal through it for at least two weeks straight. Enjoy the adventure!

Electronics (let alone cable) burn-in is another of those audiophile myths. Believe in it if you want - it is free world. My advice is to relax and not worry.

Willemj is right! Burn-in time for electronics and wire is a FALLACY.  A fancy word meaning "a mistaken belief". The proliferation of DAC's (some of them quite pricey!) in the belief of their superiority over one-box players is again a mistaken notion! It is just another ploy to extract money from the gullible! Capitalism is a savage beast that devours its children!

I quite like capitalism, but with Pareto I would claim it requires a transparent market. These monopolistic competiton tricks by boutique manufacturers claiming differences that do not exist are a scam.
As for DACs, I am usually listening to the internal DAC of a Chromecast Audio, and even on a very revealing system (Quad 2805 speakers) the sound is fine. DAC chips cost a few dollars only, if bought in quantity. Designing their implementation is a piece of cake if you just follow the instructions of the DAC manufacturer. Of course there are DACs that  measure better, but the critical question is if they sound better when observed under controled conitions.
My other DAC is an ODAC.