You should push to have your yearly scans continued. These ascending thoracic aortic aneurysms tend to grow slowly but they DO grow; unless you die of something else, the probability is very high that you will need surgery in the future. Literature from the Cleveland Clinic indicate they grow about .07 cm a year but the range varies. It is not wise to discontinue scans.
That said, Losartan at 100 mg is good. We could not keep my husband's blood pressure under 120/80 when he was taking 50 mg twice a day plus a low dose beta blocker (25 mg). The 25 and 50 mg are short acting. The 100 mg will last 24 hours. I found this information in an article on PUBMED. When I mentioned this to my husband's primary care doctor, he looked at me with his eyes wide and said: "I never thought of that but, of course, the kinetics make sense."