HEART VALVE REPLACEMENT

My Dad recently consulted with a surgeon. He was told that he needs to have the aortic valve replaced as well as 3 bypasses. The surgeon recommended a tissue valve rather than a mechanical valve, stating that Dad is 61 yrs. old and the average life expectancy for males is 76-78 , so there was a good chance of the valve outlasting him. Is this accurate? And is there more risk involved with getting a mechanical valve and having to take coumadin?