This is one advantage of balanced cables. The shorter you can keep the speaker cables, the better (more resolution, more impact). Preamps that have a low output impedance can drive longer cables, so some single ended preamps will allow up to 20 feet (although that is rare). For the most part, running longer cables than that is best done with balanced lines. My cables at home are 35 feet.
Vibration in the tubes is generally **not** a problem!
Vibration in the tubes is generally **not** a problem!