Not sure if it was the Magni or Modi (as I got and tried them as a pair), but I noticed a large change after a couple hours. I actually immediately listened to them out of the box and thought they were rather shrill. So I left them playing for an hour or two while I went to watch Doctor Who then came back and listened again.
I couldn't say how long the change took, it might have very well been after 10 minutes, but it was at most a couple hours. Beyond that they sounded similar enough that I couldn't say with any confidence that they changed any further in the next few weeks until I sold them.
Same here, but I only had the Magni at the time. It was terrible out of the box with the Q701. I didn't really want to mention anything or else people would whine about burn-in or something. They also claim that since it has no op-amp there is nothing that would need burn-in. I just know that it sounded much smoother after the first week. Weird. Yeah and it's now fine with the Q701.
Didn't hear any changes with the Modi. Sounded great on day 1.