Just as well as speaker break-in; why wouldn't they break-out ?
The industrial biz relies on standards, specs and data sheet with tolerances.
If your speakers would break-in, that would clearly mean that the specs change over time and quite rapidly; exactly what makers hate because out of industrial specs.
In other words, what you claim is that every speaker (even if same model) would sound different one from another, then be careful if you swap your left and right speaker, because they wouldn't sound the same (as you have different wall interactions) , right ?
Now it's true the some materials and yarn spec's properties change even when just exposed to light.
Advanced yarns such as aramids, (you know the Yellow Kevlar woofer) tenacity weakens over time; but that (should be) negligible.