Not so much the 3800, as we well know...

But with cars in general, I have owned a few, and with ALL of them, it seems coolant is slowly lost. Even with no apparent leaks internal or external.
I have had cars with 2.6 mitsubishi ( an old K car), 2.2 chrysler, 3.8 series II, 3.0 ford.
I am always real tedious about watching fluid levels and condition.

So is it normal for most engines to lose just a bit of coolant over time? Yes we know of the 3.8 issues, but I would be hard sold on hearing that MOST engines have the intake issues :? Especially the 2.6 Mit.
Perhaps with the coolant getting about 200 degrees, the water or coolant very slowly evaporates and finds its way out of the reserve tank?

How much do I tend to lose? The level will go from "max" to "min", at regular operating temperatures, over several months. Maybe 3 or 4 months.

I duno for sure, but logic to me says that at least SOME of it will be lost to evaporation.