It really depends on the person's medical history/other health issues, treatment, etc. You should speak with your physician regarding this.
Karen McPartland, RD
People have bypass because somehow their arteries have clogged up.
It's important to make life style changes inorder to prevent the arteries and bypass from clogging up again.
I exercise more, take high blood pressure pills, take cholestorol reducing pills, take aspirin, stopped smoking, and eat better food.
As long as you do the things needed to prevent them from clogging up again, don't worry to much about how long they "last", as most have lasted a long long time. People tend to die of other things then die of a "failed bypass". I haven't heard any news stories of a person dying because their bypass was too old.
But I have heard of a few people having a second bypass surgery over 20 years after the first. So don't worry about that, the "worry" alone is more deadly.
P.S. - Watch out for them buses when your crossing the road.