I'm amazed at how many so-called objectivists will deny break-in is a real-world phenomenon.

When I buy new drivers (woofers especially) and measure the T/S parameters straight outta the box, Fs is often considerably higher than spec...If I run the driver with some good bassy music for even a few minutes, the resonance frequency approaches spec...that's just the physical break-in of the suspension/surround etc and maybe the motor in some cases (I doubt it, but maybe). By 10-20 minutes of music the driver quits revealing any changes in Fs beyond trial error and is broken-in for all intents and purpose. I'd say most take a good 4 minute song, but subs need a bit more - volume dependant of course.

Measuring them again after months of being idle doesn't reveal anything suggesting they need to be broken in again, but I think it's a logical assumption that at least some resistance to cone movement is present the longer a woofer enjoys resting in a fixed position.

Woofers can sag over time. Though in most cases, the suspension is more than strong enough cripple the effects of gravity. When it comes to subwoofers, which are obviously heavier, we usually crunch a bit of math to calculate driver sag using gravity as a variable...if the sag is greater than 5% of the driver's excursion - increasingly less common these days - a sub will experience noticeable sag and can't be used in downfiring or upward firing configurations, but if it's worth its salt, standard upright placement should be immune to gravity effects. In many cases, sag in a downfiring position will still be only a few %, that's a few % of a few milimeters, extremely tiny, and inaudible for all intents and purposes. I suspect manufacturing tolerance variances from one woofer to the next would be larger than sag effects.