I don't think that you should be asking about what is "normal." You should instead be asking whether your revisions are improving your paper. If your revisions are improving your paper then it's good to make them. On the other hand, there can come a point where your revisions are actually decreasing the quality of the paper. The most common cause of this is that you add things to the paper that don't really belong in the paper and actually clutter it. If you find yourself doing this then you should train yourself to resist the temptation to try to say or do too much in one paper. But if you are improving the paper then it is unproductive to worry whether what you're doing is "normal." Maybe it's not normal, but if what is normal is not good then why be normal?