I understand your question in two parts:
a) do others hear the same and
b) if yes, why?
a) I hear the same, starting with and a long time with Maggies. The "simpler" ones had film caps, so no "real" cap forming was involved, and the degree of this speaker break-in is more and different from what I ever heard in caps & electronics. The Maggies sounded thin before "moving", my actual ribbon hybrids (dynamic bass to 400Hz) sound somewhat murky or "cloudy" when off for a certain time.
Leaving the system off for eg. 10 days necessitates several hours of gymnastics, the more the better.
b) as to why: I suspect the murkiness of dynamic drivers ( :-) improve a lot with gymnastics - but think about the damping, the mechanical hysteresis of the spider and surround, and even the membranes...
Interestingly Maggies, that have almost no damping, providing sort of a "clean spring" within the thin mylar foil, improve. Here it's probably a slight relaxation of that spring, probably affecting all planar speakers - ... including the newer plastic foil based Heil AMT drivers...?
Additionnaly to this there is probably a certain kind of static build up of magnetic remanence within generators, pole pieces, traces of magnetic metals in contacts (nickel) and contact supports. This is probably kind of ho-hum demagnetized by music signals.
And moving a speaker (or other audio gear) from one place to another kind of takes time and energy to adjust.
In short: I hear the same and just don't listen too focused for several hours of reconnecting a system (instead: keep on playing music in a gapless mode... :-)
