Just my $0.02
I generally don't believe in speaker break-in, but.
When The Speaker Company was around, they had a sale and I bought a pair of their floor standers and book shelves.
(They were the old Sapphire speakers)
http://forums.audioholics.com/forums/loudspeakers/52094-speaker-company-tst2-floorstanding-speaker-review.html
They were priced so low I couldn't past it up. Just something to use in a spare room.
Long story short. I hauled them upstairs, set them up and put in a familiar CD and instantly hated them.
I walked downstairs pissed that I'd wasted money, not realizing I left the CD playing.
About an hour later I went back upstairs and replayed the CD to confirm my suspicions, before sending them back.
The second time they sounded fine. I didn't get used to them, because I couldn't hear them downstairs.
For me, in this one instance, I experienced speaker break-in. Probably because they're cheap speakers?
The surround is a flexible joint, not unlike one in a new baseball glove.
Don't think speaker break in takes very long at all in comparison to a glove.
That's my story and I'm sticking to it.