2-3 times a week seems like a reasonable amount. You are right, a lot of people(like yourself) may do it for years without ever experiencing any kind of pain. Your posture and sometimes the type of shoes you use, also influence. As far as being a vegan, I can't comment much on that since I have never tried a fully vegan diet for a long time. But I do believe that as long as you're able to get enough of all the nutrients your body needs, you will be fine weather you're a vegan or not. ;)