Long Speaker Cables with Tube Amps? Bass Response

There is a gorgeous, well reviewed Tube integrated that I am interested in getting, but my home system setup requires that I use speaker runs of approximately 15'. It has always been my experience that shorter speaker runs produce superior results with tube amps, most notably in the bass, presumably due to greater damping factor. Does anyone have experience with Tube amps and long speaker runs? I am using Synergistic Research Designer Reference FX interconnects and Alpha Quad Active speaker cables. The integrated in question is the Cayin SA 88T / KT 88. Thanks for any insights.