You can have as many as you want, as long as you stay within the limit of R33000 per year. So, you wont be able to invest R2750 into each every month as that is double the allowed amount every year. You are only allowed to invest a total of R33000 per year into ALL your tax free accounts combined.
You can take the money out anytime you want - just remember the money you take out - can never be put back. For example, if you invest R33000 this year, and take out R3000. You cant invest the R3000 again into the account tax free. Any amount over the allowed limit is taxed at 40% as far as i know.