I love my Russian, its a grab and go Rba, same as the kayfun, its a good solid tank, coil I Dont bother changing I think its been 3 weeks now, I do however rewick it regularly, takes about 2 mins to dry burn the coil and stick another batch of cotton in fill the tank and go.
I've heard of issues w the kraken. I Dont know from experience.
I love my rda's and the magma has deep wells doesn't need the constant refill but yes more then the rba way more, although theyre not the hassles I was lead to believe either.
I love the better taste of build your own convenience and ability to clean and go, less expense and time.
The only time I had a issue was when I didn't pay ATTN and the locking ring wasn't on and it was hot although the battery did not vent, was at 2.4 eek but was just fine.
You have to be careful but..
Coil building is fun & addictive.