I think we're all on the same page. What I like about here more than some forums is that we can all disagree and DISCUSS our differences of opinions without flying off the handle.
I appreciate the info from Cummins, but I'm not sure the same theory holds true for all turbos. Again, I'm not promoting shutting down directly after a heavy load. My philosophy is that, normally (99% of the time) I have a portion of highway, decel. off an on-ramp, stop at redlight/stop-sign/etc, and then a short period where I pull in and actually park before shutting the engine down. In these cases, such as on the NJT, I-95 or even on a back road, I'm rarely going 0000-to-the-wall just prior to pulling off, so, regardless of convective/conductive heat transfer, there simply isn't a need to idle to cool down.
The best cooling my engine/turbo will ever see is while cruising at-speed, with full airflow through the hood scoop and through the radiator. Sitting there idling will only increase under-hood temps - not that this has anything to do with turbo cooldown.
I'm going to agree with the Cummins article that shutting down after FULL LOAD operation might have a deleterious effect, though, with my (and I'd wager most driver's) driving habits it's a moot point. Besides, how long would a tiny, alloy wheel take to cooldown to idle EGT's? I ask because I don't know. I also don't know whether the cooling from wheel to shaft to coolant is sufficient in ALL circumstances, but, in my scenario, the risk is not worth sitting there burning 0.3 gph to me.
In the end, turbine cooldown falls into the peace-of-mind category of engine care and maintenance, in that it might be good and is definitely NOT going to cause any harm. There are certain over-maintenance trends that will probably do good, and in some cases are absolutely necessary, it pays to over-maintain (e.g. ATF changes, more-frequent oil changes, PSF changes, brake fluid changes.) Others, however, are more likely for peace-of-mind only, and while they don't cause any harm and may provide minor benefit, they really only add cost for minimal gain (e.g. excessive idle time to warm up, additive use, cooldown times, especially for N/A vehicles.)
It feels good to do right by our vehicles, and I'm certainly not known for under or even only adequately maintaining my vehicles, so everything I've typed may be a bit hypocritical, but that doesn't make them any less true. We all pick that which we deem necessary to overmaintain, maintain per the book, and what we probably neglect more than we should. Most times, unlike some of our philosophies on turbo cooldown, they're based on anecdotes and personal feelings, not anything practical or empirical.
