I am using an IMR 18490 with a 1.9ohm HH357 @ 4.2volts and it lasts me all day. I do not even have to switch batteries to my 2500's unless it is the weekend and I vape more through the night. I vape all day at work and when I get home. I go through about 3.5ml a day. Before the 357 I was using a SRJoye510 2.2ohm at 4.5V and got the same performance. I think it has a lot to do with the wattage you are at.