I get that with vanilla flavor. Three hits, and bang, just this bland tasteless clouds.
I must say I mixed up a cinnamon vanilla and the first few hits are so delicious then after a few more the vanilla fades further and further till I am left with a straight cinnamon shot! So now I end up just dripping a few times every other week when I need a flavour break and when the vanilla disapears I throw it back into the cupboard.