Turbo's, to cool or not to cool.

I am sure this subject has been discussed before but for the benefit of the new comer's on the Forum I decided to raise the subject again. The reason for this is as a retired diesel mechanic and in my travels, this subject often comes up. It appears that these days the general belief is that it is no longer necessary to cool a turbo before switching off the engine. It also appears that dealers, when selling a vehicle, when asked about this they are telling the buyer it is no longer necessary to cool the turbo. The first question I ask people is, have you read your hand book? the answer is in most cases no. For those who may not know how a Turbocharger works I will explain the very basics. It is a very simple device made up of two chambers with a shaft running through both, the shaft runs on bearings and each chamber is kept separate by seals and on the shaft in each chamber is a turbine similar to what jet engines have. The shaft bearings and seals are lubricated by oil pressure fed by the engine oil pump. This device is driven exclusively by exhaust gas flow through one chamber while the turbine in the other chamber compresses air flow into the inlet manifold or via inter cooler to the inlet manifold. When driving, especially under heavy load the turbine spins at a very high RPM and the heat of exhaust gas is very high. It is not unusual to see turbo's on large stationary engines under load glowing cherry red at night. So what happens when the engine is not allowed to idle before shut down? Because of the high RPM of the turbine it will take a a few seconds before it stops spinning but more important is the oil delivery has stopped and the oil left in the turbo can if hot enough boil. This in turn starts to cook the seals sending them hard and shrink and in time oil loss past the seal. I am aware of all the ifs and butts with regard to all of this and don't intend to argue with anyone. The bottom line is what dose the manufacturer say in the handbook? have a look for yourself, I have yet to find a handbook of a turbo vehicle with no reference to the turbo.