I do. Two 6 meter pairs from preamp to amp. Good question (your 2nd to last one). I have one 6 meter pair of Discovery Signature IC if you are interested.
Who uses long interconnect like in dealers?
Ideal setup has front end components close to listening chair and run long interconnect between pre and power where power amp sits in between speakers; I have seen many high end dealers to adopt this setup and result is usually more than great. This way front end components do not obstruct speaker imaging and can also avoid bass heavy (vibration) location. But if that is ideal, why do I rarely see long interconnect for sale in used market? I don't think people only upgrade components and short interconnects?