Ha, thanks for the math Rick. id been meaning to work that out, cause I'm nerdy like that. I've come to the conclusion that I'm just a spoiled brat as far as needing fresh coils. When I use carto tanks I just have to change the carto every 2-3 days. I can't stand to use them any longer than that. It may be my all day vape that I'm using. It has a 'natural' flavor and some caramel flavoring. It may just cook into the coils more than some other juices. I buy the cartos 25 or 50 at a time from surevapes, so they are inexpensive. I think, it comes out to $1/carto, so $2 a week isn't really anything to complain about after what I used to spend on cigarettes.
One of the appeals of the protank was the ability to dry burn and rebuild, so a gunked coil doesn't end the usefulness like it does with a carto. The money savings are nice, but the main appeal is that I can refresh my juice delivery myself if the FDA does something idiotic. Hopefully they won't, but I could just envision myself watching my nice stash of cartos dwindle away with no way to replace, and having to vape on cartos that taste like old gym socks to me, LOL. Highly unlikely, as I'm sure I could find some way to get my hands on them if FDA shut the whole thing down.