No, a stent does not necessarily mean that you are near the end of your life. A stent can function for many years. Also, if new blockages in your coronaries would form, they can put in another stent. I have collected 5 stents so far and feel quite good.
The massive heart attack and also your other issues will, when you approach it statistically, have a negative effect on your life expectancy, but hey you are not a number in a statistic table! Individually, there are a lot of exceptions to the rule.
I also asked this question. It is because we want to have control. What we really need to do is to leave it in Gods Hands and say: whatever He does is okay with me.
God will call us at exactly the right time and when that will be is hidden for us and often comes when we least expect it. Until that time arrives, the best we can to is be alert and pray (Mark 13:33)
God bless!