Is there a length limit for Turntable cables?

I need to move my turntable to a more vibration-free location; or isolate it better from floor vibrations. Currently, my MMF5 works well near my preamp. However, I like the sound of my garage-sale-bargin Thorens TD160 much better and want to replace the MMF5. But if placed where the MMF5 is the TD160 is highly sensitive to vibration. The MMF5 currently sits on a 2" maple shelf which rests on Vibrapods on top of a wooden cabinet which sets on a carpeted suspended wooden floor. So, I'd like to move it to a very stable location nearby; or, isolate it better in its current location. If I relocate it to the more vibration-free location, however, I would need a 15 foot interconnect between the TT and preamp. Is that too long a distance for a TT interconnect? Will that long a cable degrade the sound significantly? Any suggestions for isolating it better in its current location.
Also, I'd like recommendations on good TT interconnects and would like to keep the cost low.
Thanks for any suggestions and comments.