Fuel Stabilizers

Should I be using a fuel stabilizer?  We've had our boat for 12 years, and even though we don't cruise a whole lot, we run the engines every month for 30 minutes or so.  And the times we have cruised to the San Juans, or even out to Lake Wa, we've never had a fuel related issue.  A co-worker owns an RV and they can't believe I don't use a stabilizer, and highly recommend it.  Does anyone have an opinion?  Am I in jeopordy if I don't?  I've got twin V8's that use gasoline, (2) 110 gallon tanks.  I'm thinking maybe they have to because of the ethanol used on dry land.