I'm afraid your vet is unfortunately misinformed. The first six months you go through (after getting your pet microchipped, vaccinated, and blood tested for rabies antibodies*) is the ONLY six month wait you have to go through. I'm sure someone will step up with more info, but you should look through the rest of the pets thread because it is incredibly helpful. :-) Good luck!!!!
*Specifically, you get your pet microchipped, vaccinated and then wait a month to get blood drawn - when the results come back, if they are acceptable, you have a six month wait *from the day the blood was drawn* (so it may take weeks to get results back, but you don't lose that time). I believe it is also possible to draw blood the same day as the vaccine (or a day later, or a week later, etc.), the thing that really matters is that your titers come back above a certain level.