Driver compliance continues to change slightly until the internal temperature and humidity within the cabinet reaches equilibrium with the home environment. After that, it should remain stable.
The same thing happens to a garden hose; it's more flexible when filled with heated water than with cold water. (I see this quite often during the Summer here in Tucson; hose is stiff in the morning and flaccid in the afternoon) D'oh!
Rubber surrounds, spiders, voicecoils etc... are all very stable and durable, and should not change their nominal compliance or resonance unless something structural is changed.
ie: if the rubber surround material is exposed to a strong chemical solvent, it might become more liquid under stress, and thus change its nominal compliance as the rubber migrates.
But normal flexing back and forth does nothing to it (and shouldn't), unless the rubber was stored in a very cold environment for an extended period. (in which case it simply warms up to the new environment in a few hours and stabilizes.)
Speaker break-in is largely a myth, probably rooted in the temperature differential I mentioned.
