I'm about to start refilling my Blu cartridges, I used to buy them prefilled at walgreens for $16 a pack, I need to quit that, so I'm going to start refilling them with mostly PG based Johnson Creek JC original tobacco flavor juice at 24% nicotine, I have 20 used cartridges on hand, so with that how many refills can I expect to get out of Blu cartridges? Thank you