In general, becuase of the kinds of results, you don't want them facing each other squarely face to face either. The exception is something like macro photography or small items in a small softbox.
If your strobes are facing directly into each other, if the subject steps forward even a little, all kinds of things like shadows under the eyes, nose and chin start to appear. Thats why we tend to set them off at 30-45 degree angles. That way the subject has a lot of room for movement without harming the shot.
And no, it will not harm the strobes at all.