@larryincmh if single ended works for you, it works, if it does not, it does not. A long single ended cable is often bad, not because it allows you to pick up more noise, because realistically, who has big noise generators near their audio equipment, but because there is higher resistance in the ground connection which could translate into ground loop noise. If you do not hear it, then don't fret about it.
If someone with some basic understanding of electrical properties and audio systems designed your speaker cable, and is not trying to trick you, then a bit of length in your speaker cables is unlikely to make a difference in the sound. If you are running Maggies and your cables have a lot of inductance or you are running Wilsons and you have a lot of resistance, there could be an audible difference between a short and long cable. If your cables are some esoteric but poorly designed cable where the resistance is equivalent to 18awg, then I would be shortening them from 12 to 6 feet personally. They may sound different. It could be worse or better.