Honestly it is recommended to NOT try extreme overclocking on budget boards for 24/7 use, especially on air. They are budget for a reason, and there would be no point to buy higher end boards for overclocking if they were just as good. They are constructed out of lower quality components overall usually. I refuse to recommend to someone that they should try to hit past 4.5ghz on a budget board like this. I wouldn't want to be the cause of someone destroying their computer because of bad advice. If someone buys a board that is manufactured with high end overclocking in mind, and they have adequate cooling to do so, I have no problem with it. I'd even try to lend a hand, lol.
Recommending a lower end board for high end overclocking to me would be no different than recommending a Coolermaster PSU over a Seasonic PSU, and expecting the same quality. It just wouldn't make sense, and could be incredibly stupid, not to mention dangerous, lol.
PS: If you haven't noticed, I have a i5 4690k and I have a much higher end board than the PC Mate. Even with this board I have to set 1.35v for 4.8ghz, 1.325v for 4,7ghz, and then I drop to 1.27v for 4.6ghz. That final drop keeps my temps at 70c max, and the other settings hit between 80-85c. That is in the winter as well in Canada. I personally wouldn't want my chip running over 80c, 24/7 365 days a year, and that is why I dropped back to 4.6ghz and let it be. The chip is not a bottleneck either way, and would very much like to keep this computer for a few years so I am playing it a little safe for now. If I grab a water cooler, then I might try going higher again.