I have a bit over 500 hrs on my '18 CW28, and a fair bit of it has been at low RPM's in the canals in upstate NY. I am not aware of any turbo issues at that RPM. As others have said, you should run it hard for at least 15 - 20 mins per day.
However, I wonder why the fondness of that power setting? I tracked and recorded RPM, speed, and fuel consumption across the operating range after getting the boat. At 1800, I see a dramatic decrease in efficiency compared to any lower RPMs as you're getting into the plow mode. At 1800R, I saw 7.2 kts at 3.3 gph, or 2,2 nmpg. That's a lot of fuel for how fast you're going. You can get a bit better mpg doing 19 kts at 2900RPM burning about 8.1 gph. Some alternatives to consider:
1800, I saw 7.2 kts at 3.3 gph, or 2,2 nmpg.
1600, I get 7.0 kts at 1.9 gph, and 3.7 nmpg.
1400, I get 6.0 kts, at 1.3 gph, and 4.6 nmpg.
You could slow to 1600, lose only .2 kts of speed, and almost double your fuel efficiency. I generally run between 1350 and 1500 in the canals, varying once an hour, get 6 - 7 kts, and average about 5+ nmpg doing so. Make sure your tabs are full up. Hope this helps.
Mike