Dog owners weighing the cost of titers against the seemingly lower cost of a possibly redundant booster should consider the estimated numbers of adverse reactions to immunization and the cost of treating an adverse reaction.
Time Out: Rabies Researchers Assess New, Long-lasting Vaccine NEWStat, American Animal Hospital Association June 25, 2008 http://newsmanager.commpartners.com/aaha2/issues/2008-06-25/index.html "A rabies vaccine and vaccination schedule with a seven year DOI will reduce the number of animals that develop adverse reactions following immunization, which is currently estimated to be 1-3% of the population."
Based on the estimate of "…more than 72 million pet dogs in the U.S." from the American Veterinary Medical Association U.S. Pet Ownership & Demographics Sourcebook (2007 Edition)http://www.avma.org/reference/marketstats/sourcebook.asp, the currently estimate 1-3% of the population adversely reacting to vaccination translates into between 720,000 and 2,160,000 dogs.