Hi Bumpy and Welcome to the MM Family

Congratulations to your son on his long success living with MMD.
You are correct in that no one knows how long any of us have on this earth regardless of MMD. With that said, the truth of the matter is that MMD is still considered rare in the medical community. As a result, unlike your son, many have gone misdiagnosed or undiagnosed and have suffered the consequences. Some have had strokes, hemorrhages or didn't survive. Some also have co-morbid conditions that make things even more difficult in terms of a positive outcome.
I would love to say that MMD is diagnosed and treated in a timely manner and like your son, the outcome is good, before the individual experiences strokes, hemorrhage etc. However, that is not the case for many. Unfortunately, your son is the exception rather than the rule.
There have been other MMers diagnosed and treated early who are doing well and living life to the fullest and have lived pretty much symptom free for years. On the other hand, there are many MMers, like my brother, who went misdiagnosed for 4 years and experienced a dissected carotid artery, two strokes and a hemorrhage and it is only by the grace of God and the hands of a skilled, knowledgeable and experienced MMD surgeon that he is alive and well today.
My brother sufferred the consequences of the strokes and hemorrhage and couldn't speak and didn't have abstract thinking ability. After two STC-MCA bypasses, he went through a rigourous rehab program and today can speak and has most of his abstract thinking ability. It's sad he wasn't diagnosed sooner before all the damage occurred. MMD has forever changed his life. Nonetheless, he decided to get busy living rather than busy dying.
It sounds to me like your son may have had a EDAS which is an indirect bypass. He most likely either had an indirect bypass or a direct bypass known has a STA-MCA.
It also sounds as though your son was very fortunate in that he was diagnosed and treated early before sufferring an major episodes.
I'm a positive, upbeat individual and an optomist but clearly, the reality of the devastation of this disease, misdiagnosed and untreated in an untimely manner is all too real for many.
Your son does bring hope to those that are faced with this disease and your son is proof that if a MMer is diagnosed and treated early by a knowledgeable and skilled MMD surgeon, before any major episodes, there is great hope for an active, long and full life.
My hope is that the medical community will take notice of this disease and realize it's devestating consequences if not diagnosed and treated early and in a timely manner.
Thank you for sharing your son's uplifting story. I love to hear success stories like your son's. I wish your son the very best for continued good health and many, many more wonderful years. My hope is that the future holds the same good fortune for other MMers.
Lore