@Kusie To be honest in my experience dry burning and changing the wick every 3-5ml for NET's is not unusual as NET's (no matter how well they are initially filtered) are known to be coil gunkers, and especially so if the NET has added sweetener, deserts etc. I have tried dozens of tanks over the years and it has always been this way. So, I really don't think you are doing anything wrong at all. It's just the way it is with NET's.
I think you may get a little more wick time if you vape at higher watts than most of us MTL vapers typically do, but I've never vaped oved 15 watts so I am only guessing on that one.
I use cotton bacon v2 for NET's as it has no break in time whatsoever and the flavour is there from the first vape, which is important if you are only going to get one tankful per wick. The pouch looks small for the money but it does last quite a long time and worth the money to me for the reason stated.
The good news is that the Doggy is the simplest tank I have ever used for rebuilding and it takes but a few minutes to quickly dryburn and re-wick. I currently have 4 Doggys on the go and re-wick them every morning during my first coffee. It's a small price to pay to maintain that great natural flavour.
Vaping is so variable and ultimately subjective so everyones experiences and opinions differ with the same equipment. For this reason I stopped posting on vaping forums a long time ago, but I saw your message and just felt I had to answer. My advice though, stop worrying, change your wick every tank and continue to enjoy your NET at its best.