Just as others have said, it depends on the reason you're doing it, and whether the coaches are okay with it. We do it because of location and also the convenience of the tumbling times. As working parents, convenience can mean a lot! We do some privates at our gym, which are great, but they do get rather expensive, and the extra practice at the other gym is a lot more economical for us. The coaches at both gyms know who we are and what we are doing, so it has worked out well. I think that just as long as everyone is on the same page and there is "perfection before progression", it is okay.