My understanding is that 2 mins is the optimum period for reduction of temperature so that stabilisation (equilibrium) occurs in the hot section, and consequent carbon build-up is obviated in the oil system. I don'tknow if it is advised in teh RFM, but I DO recall a discussion with an Allison engineer years ago who said that much more than 2 mins will see an increase in internal temperature of the turbine. Don't know if one would see this on the tot gauge, though. Someone correct me if I am wrong? Thx - VFR