The short answer is: NO.
Once you’ve put money into a tax free investment, it counts toward the R33 000 annual limit and R500 000 lifetime limit. If you withdraw any of it, you can’t replace it and still get the “tax free-ness”.
So, although you’re allowed to withdraw money any time, without paying penalties, in the long-term you may end up losing out in another way – i.e. by not getting the full benefits of tax free investments.
If you intend to, or think you may need to, withdraw money that you have invested, you may want to consider an investment that is not tax free instead.
It’s also worth considering that the longer you leave the money in a tax free investment, the greater the benefits of that tax free-ness.