In answer to your questions:
I'm on city water. The hot water is created through a tankless coil
arrrangement on an oil-fired furnace which also provides a closed loop
for baseboard heat. The furnace is in the basement and the problem
faucet is on the second floor through a total run of about 25 ft of
copper pipe. Water out of the faucet is not scalding hot. I don't
know the actual pressure, but with everyone in the neighborhood
watering their lawn, I have never had a problem getting adequate supply
of water in the shower so I assume that the pressure is pretty high.
The washers never appear nicked or torn, just a fairly uniform ring
where it is being compressed by the seat. I noticed that after only a
few months of use, a brand new seat has almost a sandpaper like
tarnish/coating to it. The washers I use are red and very hard when
new, I have tried the softer black washers but they don't seem to last
as long. No grease is being used on the seats and the threads are
being wrapped with a few layers of tefflon tape.
Any thoughts on "no-rotate" or swiveling washers. I'm thinking that
maybe the sandpaper texture to the seat is creating abrasion against
the washer and wearing it out. Anyone ever tried these no-rotate
washers? Any installation tips would be greatly appreciated.