I have been taking 20mg of Lisinopril and 5mg of Amlodipine [repl...

I have been taking 20mg of Lisinopril and 5mg of Amlodipine [replaced Felodipine] for more than 5 years.The only physical complaint that I can directly attribute to these drugs would probably be the dry cough in the back of my throat. Other symptoms such as general fatigue and insomnia could possibly be attributed but I don't know for sure. Recently I visited my doctor and asked him what would be the perfect number for both systolic and diastolic pressure for someone of my age [I am male, aged 60]. This question proved unbelievably difficult for him. After much prevarication we somehow agreed between us that systolic between 140/145 and diastolic between 80/85 would be good numbers.I then told him that I had stopped taking the Amlodipine [I don't like cocktails] for over a month. Also during this period I had taken blood pressure readings twice a day and apart from a couple of spikes I was satisfied that my numbers were acceptable. He then said that unless my BP monitor was calibrated once or twice a year [it is not calibrated] then I could not rely on my readings as they could easily be 5 - 10% out. Is this correct do BP monitors have to be calibrated to be accurate? Since I thought my BP readings were acceptable my intention was to lower my intake of Lisinopril and eventually stop using it altogether. My hope was that exercise, diet, supplements etc. could replace the snake venom circulating in my body but I am no longer convinced that this is a realistic aim.