Well it depends how you see it, but on XS, maybe not common a OC but neither much extreme yet in that overclock. The 4.5 & 5 GHz LinX stable thread is in the Intel section as well with people posting 5 GHz LinX 20 loops stable results.

But back to your original question, 1,4 V is generally considered the upper "safe" limit in many threads I have seen. I would not go much higher than that with a H80, maybe max 1,42 V. There was a guy that had used 1,57 V (if I recall right) by using AUTO settings for some time on air cooling and his processor's pin pads burned and later his mobo died. So be careful. Obviously the program you run doesn't tell me anything, but if it runs fine, it probably is the only thing that matters. I've used LinX to compary GFlops on SB-E overclocks since in many cases lower OC can result in higher GFlops than an unstable OC. Good luck.