If you use the boat reguarly, and keep the fuel fresh, you should go a long time (10 years or more), between carb rebuilds. You may never need them, based upon the quality of the carb gaskets and needle valve.
I should have stated that it would be beneficial to run seafoam during the boating season and regular stabilizer during the off-season. During off-season storage, I prefer to use a dedicated stabilizer such as Stabil. Seafoam is touted to be a fuel stabilizer, as well as a fuel system/engine cleaner. I see no reason to use both at the same time during the season as my boats are run often enough before the fuel would become tainted. But I doubt it would harm anything to run both at the same time in recommeded quantities...
