Yep. It is going to be dependent on specific flavors used. Allowing the mix to rest with an open top is used to vent, or off-gas, undesired elements like alcohol and volatile (easily evaporated) compounds that have unwanted taste.
The down side of resting with the top off is you will also be loosing the desired volatile notes (many of the lighter, more floral, notes that often find in the more "fragrant" types of flavors.This can cause loss if targeted/intended flavors.
I always vape a few drops of a freshly made recipe; and if there are harsh, or unpleasant notes/tastes, then I will usually give it a few hours with the top open. If nothing offends, or if I am working on a particularly light or aromatic recipe, I will avoid leaving the cap off.