How much (stimulants) is too much...?

OK, so most of us take some kind of CNS stimulant and various other things to make the fat melt off when we feel the need. But would it get to a point where you could be taking too many of these things (ECA, clen, T2(T3!), MD6, etc…), and your metabolism is so jacked that not only do you melt off the fat, you start chewing up muscle too? Is there a point where you should maintain the amount of ‘upper’ supplements you use for fat loss? Or should we just keep on pumping it in?