It just needs a signal. Any type of signal. TV, Movies, Rock, classical, Gangsta-rap....
It does not need to be 72 hours of consecutive use either. Everything gets settled in over time, depending on the use, then you shouldnt have a problem.
If you listen to your stuff 2-3 hours a day, then a month or so and it will be at its prime. if you listen to yer stuff 8hours a day, then a couple weeks should be all you need.
as for weather or not cables NEED a burn in time, yer gonna open a can of worms with that one! some people here feel very strongly one way, and some feel strongly the other way.
I have no clue myself.
Either way, logic shows that the signal source and content is unimportant. the volume is irrelevant on interconnects as gain is not affected.
I really wouldnt worry too much about it.
you can have it on non-stop for 6 weeks, or a few hours a day. you can play any source, tv, tuner, anything, trust me, unless you put N'sync over them, you will NOT damage them.
its no biggie! Just use em like you normally would and dont sweat it.