I haven't overclocked modern CPU's that much, but what I read from one article the 6700K was able to keep steady overclock of 4.6Ghz when the voltage had been increased to 1,315. The same article notes that even by increasing the voltage to 1,4 (usually a threshold where things start breaking) they were unable to reach steady 4.7Ghz.

It might be that the article reviewer has just received a bad CPU and you have received a good one. It is generally agreed upon that CPUs have slight differences in terms of overclocking capabilities.

Another plausible thing is that the motherboard automatically increased voltage for you. If your system seems to be steady at the moment, it's most likely nothing to be worried about. You have already broken your warranty by overclocking, but for the sake of your system's longevity I would run Intel Extreme Tuning Utility (that's what the review seemed to use) and make sure the voltage won't bounce to close to 1.4 on load. Slight difference from 1,315 should be fine.

Generally though if you have reached a steady overclock and the system is able to work under load, it won't just blip and be broken on one day. If you start getting weird errors on your OS and feel like the system is unstable for no reason, then just switch the stock clock speeds back. It is also good to memorise that if for some reason the system is unable to boot anymore, clearing CMOS by removing the battery for a minute and inserting it back is the first thing to do before any other troubleshooting.