As far as I'm aware, molasses primarily feeds media/soil microbes and secondarily has some trace nutrients; and it's good or OK to use all the time.
I consider it very doubtful that sugars from the molasses make their way into your buds, that adding molasses somehow makes buds 'sweeter.'. How would that actually work? Plants mostly only use glucose, which is produced right in the the leaves, not other sugars (e.g., sucrose/common sugar, what's mostly in molasses).
Do you really want sugars in your buds? Isn't getting rid of any sugars a major part of curing?
And vaping or smoking seeming 'sweet' logically does not actually come from vaporized sugars, which if vaped (or even combusted) wouldn't be vaporized/inhaled (with sucrose having a boiling point about 700˚C, over 400˚C higher than cannabinoids). Are you sure what you consider "sweetness" is not really lack of some thing that makes it seem "non-sweet?; that "sweetness" is actually from sugars within the bud cells/tissue?