In future I will be using carb heat as a matter of course when ambient
conditions are in the "severe" area of the chart. I definitely will not be
waiting for symptoms in such cases.

Dan, I have a couple hundred hours behind the normally aspirated 0-470
Continental in C182's.
Anytime there is significant moisture in the air, the carb will ice up.
The trick is to constantly monitor the manifold pressure. As soon as you
see a one-inch drop, you apply carb heat. When the pressure comes back
up, turn the carb heat off. Repeat as necessary.
I will not fly with carb heat on constantly.
I read somewhere in the past (years ago, don't recall where) that flying
with constant carb heat moves the ice farther down the throat where no
heat will be available to melt it.
SPORT AVIATION had an excellent article on carb ice back in the early
90's. The author had all the math and discussed latent heat of
vaporization and all the other technical stuff, but he made it
understandable by anyone with an eighth grade education.