Also if you are a '100% VG' vaper then you have to take into account that some base liquids are highly viscous since they have not been diluted (pure glycerine is very thick and gloopy), and some bases have been diluted to vapeable consistency (with about 20% distilled water). So you need to
buy glycerine base at a much higher strength than you
vape, because it may have to be diluted considerably before it is usable. As far as I can see, the vendors don't tell you in advance if their glycerine base is diluted ready to vape or not. I've had stuff that was perfect to use out of the bottle, and other stuff so thick it was almost jelly. It doesn't matter either way, as long as you know.
If you are mixing it all up, VG + PG, then this probably won't matter.