A speaker that has been sitting in a truck in the dead of winter could definitely sound different than one that has been set up at room temp.
Even the T/S parameters of your drivers can change during daily use of your speakers as the voice coils heat up. However under these circumstances, its insignificant audibly, and they revert back after use.
"Breaking in" your speakers will not prevent damaging your speakers either in future use.
If you live in a cold state or country, now that winter is coming along, just leave them in the box to get up to room temp for a couple of hours before you set them up.
