Rubber Chicken,
I believe you made a slight error regarding when to use anti-ice. It should be when TAT < +10°C with visible moisture but NOT when SAT < -40°C except during descent. This because at temp less than -40°C, all the water droplets have already frozen to ice crystals thus no chances for icing. The reason why we have to use anti-ice during descent is the temp will rise above -40°C as we descent.
HS