On a BIG 450mah+ battery, resistance is a personal choice, though some are wary of going below 2 or below 1.7 with big batteries that are not mods (mods have industrial batteries that come out the way the flashlight's battery come out)
On a slim ecig, nothing LR is supposed to be used. (can damage the electronics)
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In Boges I get the best carto life by using juices with 20% or less VG (often 10% or less) as well as a couple of Vapor4Life WOW juices which are thin. I also avoid any juice that seems to drop a lot of carto-clogging flavoring sediment.
Once you get used to using Boges you could try other brands (though I do not recommend SLB) and other kinds of cartos like the dual coil ones and reservoir cartos that need a syringe to fill etc.
BTW buy a drip tip for your atomizer too! Test juices on the atomizer with the drip tip. Only put juices you like a lot into cartos. Cartos have limited lives and few bother to clean them (plus cleaning/drying is iffy)
Also - never screw anything in more than necessary to make connection. Other wise you can press the battery post in on most big battery models an trying to lift it can be risky for the battery (you can mess it up)
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How I fill Vapor4Life KR8 cartos and Boge 510 cartos
Pop out the soft cap with an unbent paperclip in the mouth hole, very careful not to catch stuffing or the wire loop.
Shake and open the eliquid
Hold a bit of tissue on the threaded end hole, tilt the carto, and add 18 drops per ml of capacity into the stuffing (Boges and most KR8 cartos are about 1ml).
Wait 15 seconds or so then see how many more drops the carto stuffing will soak in easily.
Clean up the threaded end, tilt open end down into tissue, puff into threaded end to clear air channel (Boges and the KR8 cartos I use have a defined center air channel and I want to see light through that)
Sop up any loose juice above the stuffing
Cap and let it settle - I lay it on different sides for 15-20 minutes to make sure every bit of stuffing gets damp so I won't singe the carto. if you use thicker juice than me (I use 20% Vg or less) then you may need to wait much longer.
While vaping, if the vapor gets a bit light or a bit dry or the carto is getting hotter than normal, I take the carto off the battery and add eliquid. I sometimes use a plastic or delrin drip tip as a mouthpiece on Boge and KR8 cartos (not to drip into since the juice would head for the central air channel)