I had coronary artery bypass surgery about 6 years ago. I would really like to know how long it takes the plaque that you build up to block off the veins from your leg used to bypass the blocked arteries or if the veins just collapse or wear out? actually it was only one vein and they cut it and also used the mammary artery for two of the blockages in one of the arteries.
This depends entirely on the medications you are taking and on the lifestyle you live. A healthy lifestyle can lead to long lasting grafts and unhealthy lifestyle can lead to premature failures. Typically the grafts last 10 to 15 years (http://www.sjm.com/procedures/procedure.aspx?name=Coronary+Artery+Bypass+Graft+(CABG)+Surgery§ion=FAQ) but it really all depends on the lifestyle you choose to live.
I hope this was helpful