That's a nice OC, and temps and voltage (1.260 Vcore) are pretty ideal like that.
My own chip (4770K) needs 1.27 @ 4.4GHz and even then it isn't entirely stable and can crash every few days, sometimes when just idling. Its sweet spot is 1.225v @ 4.3GHz. After that it starts to hit "the wall". The other chips I've tried (4690K/4790K) in builds for others have all clocked better.
Congrats.