No one can predict life expectancy based on coronary vessel disease. Life expectancy depends more on general health, proper diet, exercise, etc Does the doctor intend to treat the closures? I'm approximately your age, and I have a totally blocked LAD and another vessel 72% blocked for the last 6 years or more. Medication, etc. prevents symptoms and activities are within age-based reason.
Are the remaining vessels all veins? or did they use an artery from the chest also? Veins being weaker than arteries do not last as long in general. How long your remaining vessels will last is something that only God can answer, as is your question regarding life expectancy. However, there should be three options open as possibilities.
First and foremost to get your symptoms (if any) under control, medication. If medication helps enough, this may be the option offered.
Second, look at your original blockages and see if angioplasty can be used. Techniques have come a long way since 2001 and much more difficult jobs are being successfully accomplished.
Thirdly, another bypass. In other words, replace the collapsed vessels with new veins.
When the vessels closed, did it cause any permanent heart muscle damage?