I have used it for about a year now, and haven't need to change them yet. It comes with 2 brushes in the box, and I'm still using the first brush, it is not showing any signs of wear.

The main thing is that you do not need to brush with any friction. You just move the brush gently over your teeth, so they barely wear.

For me this is also why I like it. With traditional hand brushes, I'd wear them out in 3 months or so. In hindsight this was a clear indicator that I was pushing way to hard on them.