3rdI said:
you need to be giving it at least 30mins in order to avoid tollerence building up, or at least that is what has been found by Dr S in his tests.
Actually, Strassman's dose/tolerance study showed that DMT, when administered via IV at .4mg/kg, created no meaningful tolerance to itself. You shouldn't have to wait at all, although with long smoking/vaping sessions, diminished lung capacity/strength can lead to needing more hits, etc.