Even if it fails,
a) this is still an invaluable missile test, the only consequence internationally being strongly worded letters
b) Iran bases it's IRIS space launch vehicles on north korean technology and has no issues launching satellites, thus it's clear this was more ambitious, i.e a fully fledged ICBM.
c) Once again, if nk really wanted to launch satellites, it could do so with a more conservative rocket, but it brings out the 3 stage monster with a functional payload every time in order to help test and eventually design a working ICBM that can reach the continental US.
d) In conclusion, these are disguised ICBM tests.
This phase is costly and messy. The russians, the US, everybody that has embarked upon a long range missile programme has run into repeated failures. Once the initial hurdle is passed, your rockets get a whole lot more reliable. Expect another couple of failures before they get it right. By 2020 they should be able to fission surprise Los Angeles at the very least.