Zero Turn Mowers

I bought an RZ4219 around 7/1/14. I have not had any issues with the belt as many others have....."knock on wood". Several times now, I have gone to start the mower (it is a Briggs engine) only to have it immediately quit and act like it was horribly flooded. Gasoline had immediately soaked the air filter and was dripping out the muffler. I was told that the gas tank vents directly into the carburetor and that if we have a "cool" night, gas can expand the next (warmer) day and be forced throughout the carburetor, air filter, etc. I don't know a lot about engines, but this sounds unsafe to me......any helpful comments would be appreciated. (I know I could just leave the gas tank mostly empty or the fill cap loose, but other people use this mower--they often fill the tank up all the way and then the problem re-occurs.) Am I worried about nothing?