Been a while since I've flown an ATR so the following could be out-of-date and full of bad 'hotel mode' memories.
The main issue regarding Hotel Mode is the red NAC OVHT (nacelle overheat) and associated CCAS master warning which requires the immediate shutdown of the no.2 engine. This is due to an overheat detector in the right nacelle - the concern being the damage you can do to the nacelle and not the engine. When you next get an NAC OVHT warning have a look at the ITT, I seem to remember the ITT being nowhere near the limit of 785 C.
In CityFlyer I don't remember any pilots being concerned about the detrimental effect of Hotel Mode on the engine due to high ITT. The main concern was with 'melting the plastic nacelle', to this effect our SOP was to always have a pilot in the flight-deck when No.2 was running in Hotel Mode.
This overheat warning usually occured with a tailwind, but it would also occur on calm days with little/no wind. A few times I had an NAC OVHT whilst waiting at the hold for take-off with both engines and propellers rotating - increasing the power on no. 2 engine cured the warning. Sometimes we'd briefly get the warning with selection of reverse thrust after landing, fortunately this would only last a second or so.
Enjoy the ATR, it's a great introduction to airline flying.
