Do cables need to be re-broken in?

Hi,
no, only let gravity do the work. A cable must sit and take a form.

It takes 381/2 hours for re break in.

Burn-in aside, mechanical stress with new or used coiled-up cables was a factor with most of my Cardas interconnects, and a few others tested over decades. Just letting them sit plugged in and relaxed for 10-14 days, not moving them and letting them rest did result in different results with sound too. More noticeable in transparent systems primarily. Makes little to no difference in less transparent systems or low grade metallurgy and no dielectrics used in cheap cables - still sounds grainy regardless of time, YEMV. 

According to George Gardas:
http://www.cardas.com/insights_break_in.php