i have read a few things a while back about the issue you are talking about.

letting the engine idle for 1/2 minute has little to do with heat in the turbo. it's directly connected to the exhaust, so it's always getting heat even at idle. more importantly, it has to do with lubrication. the turbine inside the turbo sits on a bed of oil. there is no metal to metal contact. this helps to reduce friction while at the same time it helps the turbine spin faster.
now the turbine is always spinning when the engine is running but it spins faster as the engine rpm's rise and it takes a few seconds to spin down at idle. but when the turbine is spinning very fast and the engine is shut off, the oil pressure drops and the turbine gets less oil and thus less lubrication which causes friction (metal contact). that is why they tell you to idle the engine first before shutting it off.
the T6 uses 2 small turbos pushing very little boost so i would only wait no more than 10 - 15 seconds before shutting it off after some hard driving. you have a good practice of "NOT TO GIVE IT SOME HARD CHARGING IF MY DESTINATION IS APPROACHING".
also i would not shutoff the engine after hard driving if the fan is still running to prevent afterboil. wait til it shuts off before turning off the engine, this goes for all cars not just turbo's.

hope this sheds some light on your inquery,
Al