Odd, I think they may be other factors at play here as I exclusively use hot water. I have 3 FA wet tumblers and have processed god only knows (well over 200,000) pieces of brass in hot water and have never had dull brass. All of my brass comes out incredibly bright.
I put the 5lbs of pins in, add brass until its about 3 inches from the top, fill with hot water, add 1 45 acp case of lemishine and a healthy squirt of blue dawn dish soap. Tumble for 3 hours.
I also use very hot water, but only half that amount of lemishine.
I put the timer on for 3 hours but often 2 is enough for cases fired by me. Range pickups need the extra time to come out 'like new'.
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