Hi Jenny, Happy New Year to you, and Ian too.
We have had our 19 exactly one day less than Jenny has (3 full camping seasons), and have yet to use our bathroom sink. Actually, the shower has only been used once, and that was just to try it out (it worked fine for me, but I have no hair to wash
Most of our camping is boondocking too, but for the most part only 4 day trips, so a quick sponge bath is usually all we do (sometimes a dip in the rivers around here, but they can be a bit on the cool side). Longer trips usually find us staying more often where there is bathroom facilities that include showers.
If I had my druthers, I would have omitted the sink in the bathroom. But, it really does not take up that much room so is not that much of a bother.
Basically, I think it comes down to the way you camp, and they way you do things while you camp.