I also got the mega cartomizers, they are spendy but they work fantastic and are sooooo easy. I am on the same two carts I started with last Thursday. I just keep refilling them. I am using a syringe to fill them but it is really easy and lasts a very long time even when I am constantly vaping.
I have used the mega cartomizers also, and liked the way they performed, except I seem to notice a weird chemical taste with them. Did you notice that?
For me I just find them really easy to use. I just added one to my rotation so I fill them up, put them in my case and I am ready to go anywhere because they last so long. You might want to ask the vets here about it though.