So, according to the first video, xmax for a woofer a few minutes below Fs and it's broken in. The spider's compliance will lessen after some time, but never go back to it's original 'new' state. A few seconds at xmax every few months should solve it.
I'm in the camp that claims that some drivers are really stiff and needs the xmax treatment to be able to be articulated. My subwoofers went from boom-boom to making music in matter of few hours without the xmax treatment. That's not in my head and the part 1 video above support it.
But what about some manufacturers claiming that the glue holding the surround needs hours at normal listening level, interspersed with short periods at higher levels, to get a proper hardening?
Still, are some drivers stiff enough to require many hour of break-in? Not sure what to make of this, but a guy named Fahey(Fahey drivers?) claims to have been making and selling speakers for 35 years. From
https://www.diyaudio.com/forums/full-range/225709-break-real-7.html#post3287218
'So far, so good, but sometimes a customer says "fine, I like it, but let me test the actual cabinet I'm buying, instead of the "test" one.
So we bring a fresh one , set it aside the "Test" one, and simply plug it in.
No time lost in dismounting and remounting speakers as some have mentioned, just 5 seconds switching.
Boy, the difference is *dramatic*.
So much so, that I have
a) been accused of "testing the amps with a *good* speaker, then cheating and delivering a cheaper one" or
b) had to actually deliver the old, used one.'
'....the difference after a couple months of heavy use is *dramatic*.'