I do not support the belief that small Continentals are any more suceptable to carb ice than any other engine type. I can say that the O-200 installation in the Cessna 150 is a poor example of an effective carb heat system. Perhaps a less than ideal de icing system of the airframe design causes blame to the engine itself in that airframe.
My personal technique (borne of 2500 hours in my C 150 over 23 years) is to use the carb air temperature indicator (a vital safety instrument, in my opinion) to indicate how much carb heat to use to keep the carb air temperature out of the danger range. Other than that use, I do not touch the carb heat control at all during flight.
I do occasionally use the carb heat while taxiing, if conditions seem to promote carb ice, and otherwise only select it to check it's operation, pre flight.
I once had an engine failure upon selecting carb heat in flight. Nothing to do with ice. The change in ducted airflow allowed a mouse nest in an induction hose to be sucked right into the carb throat, and choked it completely.
Two additonal thoughts on carb heat use:
If you have chosen to use carb heat, consider doing the following right away: Reduce the throttle setting somewhat, to reduce the total mass airflow into the engine. This reduces the amount of heat which will be needed to raise the temperature of the air in the carb, and the metal carb parts themselves. It also reduces the total amount of moisture being sucked in. (this is a good reason for having an idea of the minimum power setting your aircraft needs to maintain altitude). Once set at this power setting, lean the engine as much as practical. Bear in mind, that for most engines, the power setting will now be in the range where leaning to peak is acceptable for continued operation. The hotter the exhaust, the hotter the carb heat air. The less volume of intake air, the hotter a given amount of carb heat will make that intake air.
If you're using carb heat, turn off cabin heat. Other than for aircraft with combustion heaters, it all comes form the same place, you may as well get as much as you can where you need it most...
Pilot DAR