Audioquest believes there is a break-in period that applies to the AQ Niagara 1200. From their owner's manual:
Though every attempt has been made to reduce the necessity of so-called “break-in,” “burn-in,” or “run-in” time—including high-power run-in of every critical capacitor in the Linear Noise-Dissipation Circuits—the Niagara 1200 will benefit from continuous use, just like any other audio/video component. This is not to say that you will be made to “suffer” through weeks or months of intolerable performance until that “magic day” when the parts are fully formed and ready. On the contrary, the Niagara 1200 will perform very well from the first moment you use it. It will improve gradually, in small increments, over a period of approximately two weeks. While leaving the Niagara 1200 turned on during this period will aid the process, it is also perfectly acceptable to turn the unit off; doing so will simply increase the time it takes to reach final “break-in.”