Bridgette gets bordetella every 6 months, DHPPC every year and RV every three years. We only do all three because she comes to work with me often and I could easily bring things home with me.
How often she goes to work with you or where you work has no bearing on the need for vaccines. Once she has had the puppy shots and maybe a 1 year shot, she is immune forever. Giving her shots every 3 years does not make her more immune. Either a dog is immune or he isn't and your dog is immune for life.
Titers is not a reliable test for immunity. Titers tests for antibodies and dogs can be immune without antibodies.
Some people may be afraid to say it but I'm not ... people who vaccinate every year or even every 3 years is putting their dog at unnecessary risk. You should research dog vaccinations and read the latest research.