My lovely boy had this condition, for about the last 3 years of his life. The trouble was, the vet said they have to do blood tests at least every 6 months, at times it was every 3 months, before giving more meds. My cat got terribly stressed by this procedure, I'm not sure they were very kind. One time he was so upset on the way home, I thought he'd died. It was awful to see.
I could see myself how the drugs were going with him, and if he needed more, by just watching him. I know they have to do this though.
In the end, he had something else wrong too, we never got a real answer, in spite of lots of tests. We decided he'd been through enough. Looking back, I would part with him earlier than we did.
I would just try the meds for now, and hopefully you may get several more good years together, but sooner or later you will see that he is not his old self and will know the kind thing to do.