Do speaker cables need a burn in period?

Oh yes, don't pay much attention to how they sound during this burning in period unless you want to have fun. Give them a time.

Burn them in at 110db with analog source only !
Just kidding. But use various music. Don't assume that they were fully burnt-in. Do you know how many people, not audiophiles, sell their new equipment because in fact it was not properly burnt-in and naturally they didn't like the sound !

Give them 300 hours of play, whatever you've got or going to get, and tell us what happened. The length of burn-in will vary, usually the better the cables the longer but not always.

No, just play it any way you want to.
Low flying aircraft ? Hard to compete with. A few days ago there were a thunder and lightening over here and I thought - how can any audio system reproduce that ? Or record, for that matter. Crazy audiophile thoughts indeed.

At the very least a few hours of not being moved. 
Never heard anyone report cables sounding worse after a few hundred hours.

Yeah, again. Let's add to it - silver or copper or alloy ? I prefer copper for interconnects and silver alloy for speaker cables with my particular speakers. Both are Purist fluid cables. Solid state equipment.

That would be quite an average listener. With Purist Audio cables that I have I heard no or almost no difference after 300 hours, interconnects or speaker cables. In higher resolution system - maybe. Jim Aud of Purist says 300 hours for his better cables, and I agree.