My dad was on 16 and now on 18 mg a day and the only side effect seems to be swollen feet. He is quick to anger and went into rages but then again, that is what he use to do when he was much younger. So we talked to him that it cannot healthy and although he still gets upset, who would not with the frustration of one day being able to walk 18 holes of golf at age 69.5 and what seems to be the next, not being able to pick up a cup, he is doing so in a much more controlled manner.
As with this disease each person is completely different.
Our NO is suggesting 18 is the max because they are worried about his stomach but given he is now 70.5 and realistically given the location of the tumor, we would be willing to exchange function and quality of life for time.