250k on my 2011 3.5 ecoboot and have never let them cool down. Never had a turbo problem. And I run the hell out of it.
If you have a diesel and are pulling hard and the EGT temps get way up then it may help to let them cool off but the EGTs on these are not going to kill a turbo.
Ordered 1-21-21. Rolled over to a 2022 in October. Nothing. Still sitting on order accepted.
I was down to my old 72 pick-up to drive as I sent my oldest off to college in my F150. Bought a High Tide Jeep 2 weeks ago and really like it. I'll be shocked if I get a 22 at this point.