How often, how few times to prevent damage

[INSANEPOOKIE]

Just curious here; as I am with pretty much all drugs.
Even though this question may have a varied range of answers there must be an average that one could list as a possible dosage and how frequent one could use and not harm the body.

How often, assuming the human is of average build and no overall health problems, could a male/female (if the answer would vary) use Meth and not suffer from long term physical damage? I'm not interested in any form of mental addiction, just the actual long term physiological damage.