@Bobby ***
your friend heard wrong. A year long, multi-entry Non-immigrant O visa is valid for a year <- that means you can exit/re-enter all your want for the whole year BUT every entry is good for 90 days only.
So when that first 90 days is up you either apply for a year extension at the immigration office OR you bounce out and back in to the country to get a new 90 day entry stamp and you do this for the validity of the visa (a year from the date it was issued)