Annual Vaccinations - Too Often, Or?

BETHYSMAMA asks: "I have read recently how a lot of vets are switching to a 3 yr schedule with vaccinations. I have 4 dogs that have always followed the yearly schedule, with all that I have read about the new schedule I am now worried I am over vaccinating them. But my question is, my husband works at the Humane Society he handles a lot of dogs that have parvo, kennel cough, etc. With him working there how high is the risk that he would carry home a disease to our dogs? And would it be safe for them to go on a 3 yr schedule?"