I have a Prodigy v2 w/501 atty. Been puffing away on it now for 28 hours and LOVIN IT! I have NO desire for a real cigarette and I smoked for 37 years, at least a pack a day. So, I'm dripping 3 drops onto the atty, I puff away until I get that first "burnt" taste and then I add 2 to 3 more drops. How long should the atty last, approximately?