Is bypass surgery a 1 time thing?

I had a heart attack and triple bypass 16 years ago. A stroke 8 years ago. I have high blood pressure and high cholestoral. I am in good shape . My problem is my genetics. All 10 of my aunts and uncles, grandparents and mother all passed away in their late 40's or early 50's.All from heart disease or stroke. My father is 75 and has had bypass surgey and now has a pacemaker. I take 7 different medications for my problem. I have been diagnosed with
Atherosclerosis . The surgeon who performed my bypass said I would be back. 16 years seems like a long time and I'm concerned that I may have problems again. Just wanted to know if anybody has gone longer than 16 years after  bypass surgery and if they have had any complications since. My understanding is that the veins used in bypass surgery have a tendency to get blocked again. Am I worrying for no reason?

Thanks