People are, of course, free to do what they want, but I'll make and argument again for no overclocking whatsoever. If a system's hardware is both compatible and configured properly, the gains from overclocking will be fairly minimal. If people are noticing crazy levels of improvement, that's more indicative of a configuration issue and/or OC values being extremely high.
In the end, OC will increase performance, but can also muck heavily with system timing, needlessly cook hardware (shortening its lifespan), and generally provide gains that may be next-to-imperceptible if compared to that same system configured more efficiently at default clock speeds and voltage.
I know people love to see the big numbers in terms of FPS, but also keep the following in mind:
1.) Your FPS is always limited to your monitor's effective refresh rate. If your monitor is 120 Hz, then you will never, ever see more than 120 FPS. The video card may
render 263 FPS, but it can only ever
draw 120. The rest of that "performance" is wasted: dropped frames. So, in the example above, that PC is baking its GPU, and displaying less than 50% of its performance output. (Yes, having extra frames rendered can noticeably improve response times and such -- especially if running with Vsync disabled -- but I'd recommend always using a
frame cap to ensure you're rendering only ~24 frames more than your refresh rate. In my experience, anything greater than that gives severely diminished returns.)
2.) Physics engines tend to dislike overclocking. Lots of jitters, FPS hitching, or crashing issues can often be tied to physics engines getting all wonky. Many (most?) physics engines will be based on data associated with specific frames. They try to "keep a rhythm" with game processes. One of the big downsides of OC is that it can process things too quickly -- delivering data before the
engine is ready for it, then the 3rd-party physics processing (like PhysX) gets all confused and blows up. Best way to test this is to try it with a Bethesda game. Especially Skyrim's physics are prone to all sorts of craziness if the system timing is out of sync with the engine. Great way to identify a good balance is to get Skyrim working well with the OC.
3.) Placebo effect. I have several friends that swear by overclocking, and shake their heads at me for not "taking advantage of my system".
But, these are also the same people that want to know how in the world I get games like TW3 to run
sooo smoothly...or how I manage to play Elite: Dangerous with almost no hitching or loading jitters
ever. I then explain that my TW3 is running at
48 FPS, capped. They stare blankly at me. I show them that I have Elite locked to 60 at 1080p, and my GPU is normally around 40% in-game. They frown. End result is: when people just sit down and play the game,
not looking at the configuration first, the way
feels immediately stands out. If they look at the
numbers...all of a sudden it starts to
feel like there's something "wrong". The true end result is what the gameplay experience is like, not what the numbers say. Less can very much be more.
4.) System stability, especially voltage. A lot of systems have PSUs that are not really all that well suited to overclocking. I'd recommend people invest in a good quality PSU with at least a few hundred watts over what their hardware requires. Both the power overhead and the consistency of the voltage will tend to have a big effect on how the system actually performs. I remember, when I did overclock stuff heavily in the 90's and early 2000's, a bunch of instability problems I was having boiled down to weird voltage fluctuations at inopportune moments.