Cable break in is a fact wether speaker cables or interconnects.

Speaker break in is a fact. New Speakers only sound alright. There is a definite break in period.
A break in time for all electronics is a fact especially CD or DVD. Need heated burn in time for the laser.

None of these are myths. There is a break in period for everything.

One day you will throw in your favorite CD and notice a warmer, more crisp sound that you have not heard before.

My unfortunate issue is I have a new 1070 with new front speakers so it is very hard for me to tell how the 1070 really sounds.