From my understanding once you OC you have to raise the voltage aswell correct?
No, not necessarily. You can just increase the clocks of GPUs and CPUs without touching the voltage at all, and most of the time you will be able to get at least 10% without changing anything other than the clocks or multipliers. Once you've found how high the CPU or GPU will go at stock voltage, you could
increase the core voltage (or any number of other settings) and that might
increase the maximum stable speed at which the CPU/GPU will run. There is no guarantee though, except that a higher voltage will exponentially
increase power usage and heat, and it can lead to premature death of the chip if you push your luck. What I mean with exponentially increased power and heat usage is that a 10% overclock at stock voltage will lead to approximately 10% more power usage (often a bit more), but a 10% increase in core voltage will lead to 21% increased power usage (1.1 * 1.1 = 1.21). So if you increase your clocks by 10% AND increase the core voltage by 10%, you will have roughly 33% more power usage! And all that extra power is being turned into heat on a very small surface that your cooler is trying to keep cool.
To give you an idea, I have my i5-2500K overclocked to 4.3GHz, at stock voltage. The chip can do 4.6GHz or more I think, but to get there I have to increase the voltage, at which point my motherboard starts throttling the CPU to keep the VRMs from blowing up.
lastly, what would you consider 'stable" I looked around forums and such and many people have different opinions of stable. Some say that 24 hours of prime without errors and bsod is stable others say 8 hours is stable some even say not to use prime...lol
I would consider a configuration stable if it reliably does what I need it to do. That means that a gaming PC that might crash once in a blue moon is stable for me, but a mission critical server that does the same would be unstable, because it cannot be relied on. For the purposes of overclocking, there is no 100% way to be sure that it is absolutely stable. The reason is that Intel and AMD leave a good bit of headroom because they
can't be sure either. All they know is that if you keep well away from a chip's limits, it will probably
be pretty stable. Overclocking is the art of getting closer to those limits and thereby extracting extra performance, with the caveat that you give up the big safety margin that the manufacturer left.
So, how would I test for stability? For the purposes of roughly finding the chip's limits, 10 minutes or so of Prime95 will give you a good idea. Then if I think I found a stable setup, I would test it with Prime95 for a couple of hours, and then with Intel Burn Test as well. Those two programs do a good job of putting a lot of stress on the CPU whilst verifying that they're spitting out the expected results. I would even let one of those running over night. Then, if that has worked out alright, I would either accept that as the stable configuration for now, or I would back off 1 step. Backing off 1 step would give you back a little of that big safety margin that the manufacturers left, so you can be (again) pretty sure that it will really actually be stable. If you don't back off at all, don't be surprised if you find that a particular game or application crashes and burns in a most unpredictable way.
edit: oh yeah, as Captain Ned said, if Prime95 or similar programs give any errors at all, you consider that as a failed test. Your overclocked PC should behave exactly as stock, only a bit faster. Any deviation from that is a sign of pushing it too far.