Are there easy at-home tests that would be useful data for your doctor? Is once a month necessary for this specific condition? Is three months? What about keepi

Are there easy at-home tests that would be useful data for your doctor? Is once a month necessary for this specific condition? Is three months? What about keeping records and sending them to the doctor every couple of weeks so an extra appointment can be scheduled, but only once every four or six months normally? I have hypertension. I've had it for years. It doesn't just go away, but it doesn't (at least in my history) rapidly get worse. I can take my blood pressure at home and chart it. The same medication I have always taken works and at the same dosage. Yet most doctors want to see me every two months to renew the prescription, prescribing a one-month supply with one refill. The stuff's shelf stable for a few years. Why can't I get a six month prescription?