I would think it depends on the substance. I know I stayed off my low-level usage of opiates for 6 months and my dosage never even wavered. I use blends and pot a lot. Tolerance break for me is several days to a week of non-use for either & a huge reward will be received in euphoria when usage begins again
Edit to say I'm not that great at will power, so when I stop taking one thing I like to have another thing to begin using, like a crutch.