Unless the kit wire is too short, as crassius said, there really is no advantage to replacing it. As I've posted many times before, the kit wire is at least metallic core where by comparison most ignition wire you'll find at auto parts stores today will be resistance wire. Resistance = less voltage to the plug. Why change good wire for one with higher resistance with our weak little ignition systems?
It is a very common myth that the kit wire is inferior. Unless, as was mentioned above, the insulation is cracked and the current is arcing to ground, the wire that is on the CDI is good. I do subscribe to replacing the kit spark plug and especially the boot, but not the wire.
I do replace it but the reason is I mount the CDI further from the engine/downtube and the kit wire is always too short but I replace it with copper core ignition wire as Venice suggested.
Tom