Speaker cable length for L/R channels critical?

I have a good system that utilizes some older discontinued speaker cable that I like a lot. It is 10 feet in length and I need that length to reach the left speaker. The amp is not (and cannot be) located center between the speakers.
The problem is I wish to biwire and have an opportunity to buy a 6 foot pair. The question is this: Can I run both 10 foot cables to the left speaker and run the 6 foot pair to right without any wierd effects like "ghosting" or have one channel be clearer or louder than the other? Any ideas? Thanx