Is a Dr. visit really necessary for each INR?

After 9 months of working with my father-in-laws' Dr.'s office and making them increase the frequency of the INR blood test until he was getting consistent readings and then gradually increasing the time between checks to every 4 weeks and getting consistently good readings (they were checking every 4 weeks and constantly making big changes in dosage before I stepped in), we got a call yesterday from his office saying that his INR was good and to recheck again in 4 weeks, but that the Dr. has decided he wants to see his patients for an office visit each time the INR is done.  Does this seem reasonable or am I right to question the need for this expense even if insurance and medicare will pay for it.