second surgery?

Hi, I am an active 47 year old woman with subaortic membrane stenosis. I underwent surgery in 2004 to remove the membrane and also had a resection of my aorta. I also had part of my heart muscle shaved off and my pulmonary valve had a spider web type blockage that was cleaned out. At the time of surgery, my peak gradient was 102. After surgery, it was 24. It is now up to 66, but I am asymptomatic. I excercise regularly, walking on my treadmill @ 4 mph three to four times per week. I learned at my last visit with my cardiologist that a second surgery is looming in my future. I have a few questions that I failed to ask my Dr. One, is surgery riskier the second time around? Also, what are the chances of this recurring in the future? How many times can one have open heart surgery for the same condition? How high does your gradient have to be before surgery is indicated? The first time I had surgery, the only syptom (symptom) I was experiencing was excessive sleepiness. I also failed to mention that I have three leaky valves, but they are not leaking enough to have them repaired. Thanks for your time.