I can't think of any technical reason for matching speaker wire lengths unless you were worried about tiny differences in capacitance somehow affecting your response in some infintesmal way.
IIRC, signals travel at 1/2 to 2/3 speed of light in a typical cable, ie perhaps 600,000 times as fast as sound. The finest adjustment in the receiver is probably on the order of a millisecond, which corresponds to about 100 MILES of speaker wire.
There are so many good things to worry about. This isn't one of them
