I own two of these Gaiam yoga balls so more than one person a can use them at any time in my house, and they are used often. So many yoga balls that I have used either aren't study enough or they don't last very long, but I have owned my two Gaiam yoga balls for over two years now and have not had any issues with sturdiness or air being released out of them.
Definitely the best thing about these yoga balls is that they stay strong no matter who is using them. My family does a lot of exercises that put a lot of weight on the balls, so it is nice to know that we can rely on them to stay sturdy and allow us to focus on the workout and not the ball itself. Considering these yoga balls are actually less expensive than some of the others sold today, I don't see how anyone could complain about this product.
People who regularly use yoga balls in their workouts or plan on doing it in the future should definitely look into getting one or two of these Gaiam balls. They are the best that I have used so far and I plan on buying some more if my first two ever die.