A repeat from another thread.
We had a 2010 Yukon Xl and the seat heat could get positively uncomfortable, that is, too hot. Our brand new Yukon XK also has heated seats, and the first thing my wife said about the new ride was "The seats don't get hot." (She has a bad back and keeps the seats on Max). I asked a knowledgeable guy at the dealership, who told me that GM did lower the max heat in the new models. (Don't know what year this started).
They're just built that way, apparently. Blame the lawyers.