Is it normal to not have visited a doctor in over 20 years?

There are many people who do that. However, we do not recommend it. There are illnesses which can be present without symptoms (like high blood pressure and diabetes) which are nevertheless causing accumulation of microscopic damage to the body; by the time the damage has accumulated sufficiently to be noticeable, it is too late to prevent or reverse it.

We recommend children be seen annually to age 18, then healthy adults should be seen every 3 years from 20 to 40, then annually again after that.

Well if hes healthy, doesnt drink or smoke, and has no symptoms of any kind of illness. Then i dont see a reason why he HAS to see one. But it would be a good idea just to go get some blood work done, make sure everything is okay.

I have seen many elderly patients who insist their good health is because they "stayed the Hell away from doctors". I personally think they were just lucky.

Good to know one, for when he does get sick. Might be a good idea to get checked, just to see if trouble is brewing.