I had known this could happen but I think it's not very common. My CABG was done in Oct. 2006 and I had 5 done myself. I found the following statement in MedlinePlus:
"A bypass also can close again. This happens in more than 10 percent of bypass surgeries, usually after 10 or more years."
This comes from MayoClinic.com:
After surgery, most people have improvement or complete relief of their symptoms and remain symptom-free for several years. Over time, however, it's likely that other arteries or even the new graft used in the bypass will become clogged, requiring another bypass or angioplasty."
Honestly, I wish I could give you some numbers and more helpful information. It seems that the grafts are expected, in most cases, to last 10-15 years. A lot depends on how advanced the CAD was to start with, the condition of the veins harvested for the graft and how well the patient incorporates the appropriate life-style changes. Perhaps it is influenced by dumb-luck.
Really, your best bet is to ask your cardiologist or cardiac surgeon. Don't let them put you off either. Demand answers. Sometimes they don't want to be real straight forward unless you are persistent and insistent.
If you find further information, I would love to hear about it.
Thanks for your answer. I hope it helped them. I know it gives me a little more information. Keep up the good work!