Provided all parts were performing in their best and operating under normal circumstances, how long will a system like this will last? Guestimates please.... disregard software issues.

Q6600@ 3.60Ghz, 1.5 Vcore (1.5125V in Bios) <- i tried to squeeze the highest possible speed within intel recommended
1.5V, this was actually my main concern here.
Asus P5k Deluxe Wi/fi - Most settings were left Auto/Default except mem timing and CPU speed/voltage.
OCZ 8 GB DDR2 800 Platinum - Running on default SPD
Gigabyte Pro 550W
MSI Radeon 4850
Cooler Master Hyper 212

System average use was about 6-8hrs daily,(planning later on for 24/7) CPU operating temp was average of <45C
Sytem was stable at Prime95 @ 70C reading from Coretemp.

Hardware will last as long as the hardware itself does not fail.

You might want to re-phrase your question. I'm guessing you're more wondering how long your system will last in the context of how well it will run the applications and play the games you play. If so, the system will last as long as you perceive it to be operating fast enough and as long as it runs the apps and plays your games at a level you find acceptable.

That's the beauty of building your own machine, you can upgrade the individual parts to extend the life of the machine, i.e.; add more RAM, upgrade cpu, upgrade video card, etc...

I thought he means if it will shorten the component's life.

I used this system for almost 3 years for playing games

AMD 4400+, 2gb ddr dc, asus premium sli mobo, evga 7800gt

I only recently upgraded to a x9450 quad, 4gb ddr2 dc, asus xfire x48 board, and a 4870. I am hoping this will last me as long

Yours will last as long as you can do what you want with it, when it starts to bog then you will probably start to check out new parts.

Doesn't Intel say their CPUs last 20 years?

With that OCing I'd give you at least 10.

My guesstimate:
The system will function for 10-20 years.
You will want to replace it in 2-3 years.

If he means about hardware lifespan, i am going to talk about probabilities here.
The first thing to go will normally be the harddrive, because of moving parts that ware out over time, and the plate itself becames more "fragile" overtime. Next..its hard to say, everything can go without any specific order. Assuming that nothing in the hardware is heating abnormaly (such thing will shorten components life), everything that as electrolytic capacitors will cease to work within a couple decades, because those components have a electrolyte inside of them, that dries within 15\30 years (lol@ if you will have your computer for that much time).
Even lolish, if that didnt happen, the board logics parts would work for 200 years (amount of time that the quartz controling the chips clocks would keep their precision). And above that, chips internals would work for 900 years more or less until something inside of them "rotten".
But this is the ideal world of no overheating inside of the pc, that doesnt happen at all.
I would guess that the board would go first because of its power regulators that would burn, or the videocard itself for the same reason.

IIRC they claim about 1% failure in after 10 years at stock speeds and voltages with adequate cooling. I wouldn't doubt that as I have used CPUs that were at least that old that ran perfectly fine.

Maybe, maybe not. I am edging on the side of "not" as that's significantly out of spec and drawing >2x the power of a stock chip. It might last a year or two at that voltage and speed, but I'd put decent odds on it being dead 5 years from now due to electromigration.

Good until DX11, then might have to upgrade something. 1-2 years I say

MU_Engineer every time you make a post I learn or have an oppurtunity to learn something. Reading this thread I was wondering if it was the heat or the electical charge that actually effected the silicon but now I know, thanks. So no need to explain electromigration, I found it on Wiki:

http://en.wikipedia.org/wiki/Electromigration

Eeerm there's another thread discussing a low power usage file server and a certain poster mentioned the idea of a standalone photovoltaic unit possibly powering the unit 24/7 with battery bank of course. But we need someone with an engineering background to work out exactly whats needed.

Thanks for the input, actually im refering to hardware lifespan(sorry for confusions) if i leave it as it is now for the given operating conditions. I was wondering how long will it be working without problems. I dont intend to replace my rig for maybe 3-4 years. ( also disregard harddisk since we all know this part is very vulnerable.)

I usually use my rig for some gaming, movies, music and testing environment( servers thru VMware etc.) all in one.

Im new to everclocking so im not really aware how much it will degrade the lifespan of my machine and really enjoy it as it is now. As i have said im a bit worried bout my CPU since i bump some extra voltage on it and reached intels max recommendation.

Personally I wouldn't worry about your situation at all. If you look at the system clocks and cpu clocks in competitions around the world they are VERY high, with many chips overvolted well beyond manufacturers recomendations. Also when you read about cpu's overclocked to the point of failure, they rarely ruin other components even when they do die. I remember reading about alot of blown moffsets on the X38 boards at sub zero but they claim this has been rectified on the X48 sets. Remember that's at sub zero, well beyond general air and water cooling.

Also if your Q6600 does die prematurely have a think about what it will cost to replace in 1 or 2 years, even if it was available then. It would be DIRT cheap. So all things considered, don't worry. Just remember when your overclocking if you overvolt something a little more than you comfortable with and your system doesn't reach stabilty, don't keep overvolting because more than likely your problem is somewhere else.