Do re -wired BI wired speaker cables need break in time ?

Yes, I believe that just about any cable will benefit from some break in time, despite being broken in.

How long?
It depends.
I say let them run for a while using moderate levels of music and let nature take its' course.
B 

My apology fellow members as I should have listed this under cables. My mistake..... 

I remember hearing or reading years ago, that George Cardas had stated that anytime you move or re-position a cable, it will need some time to "settle in". I took that to mean a break in period, I would guess it would not be as long as when new, but let them play for a few hours and listen for any improvement.

The new bi-wiring setup has new connectors---spades or bananas---and they need to break in before you can evaluate the sound quality.  When I change spades, I allow them to break in for 40 hours or so before listening.

Let them settle for at least six days they need burn in .

Let them settle for at least six days they need burn in .

Jayctoy  - why 6 days ? Just curious as to that number - but thank you for responding to my inquiry.

40-50 hours break in period needed at least,  Lately I bought used bi wire links and it sounded great from the beginning because my dealer used them regulary for demo sessions. 

@garebear , maybe the 7th day is for rest. ;)
B

3 years, 184 days, 9 hours and 12 seconds. You'll hear it. 

I agree they will need some fresh breaking in.  New connectors, new sheathing to split into bi-wire, mechanical stress to the cable, etc.

I have found even used Cardas may take a couple hundred hours to sound their best.  The changes tend to be subtle rather than wholesale, including reduction in hardness or glare along with increases in clarity and refinement - in short, the same complaints most people have during the initial breaking in period for Cardas cables.  We rarely think to ask the previous owner how long the cables have sat unused.  As well, the speaker-amp interface in your system likely presents different characteristics to the cable from the previous owner's.