The higher you boost, the more potential problems you run into. I'm running 8 PSI on a custom T25 kit right now, and I'm going to either see about upping it to 10 or swapping to another turbo in the future. I'm prepared to deal with the problems though, and if, God-forbid, I do blow this motor, I've got a 4G63 out of an Evo IV that will take its place.
8 PSI should be plenty for you though, it's a safe number, and it will definitely put a smile on your face. I put down 175whp and 183 ft-lbs tq completely untuned (off the charts rich) and with an exhaust leak.
Dyno graph.
I expect to be closer to the 190's or possibly 200's when all is said and done, which is why I'd also like to up the boost or swap turbos eventually, as I'd like to put down closer to 230whp.
I think amby said it best though, it's all going to depend on a number of factors. Basically everybody's going to have different results. Where one guy could boost 12-13 PSI the entire car's life, another might not be able to exceed 10 without blowing his motor. I don't mean to sound like a dick, but if that's the only question you're asking, you're probably not ready to be spooling.

 

Because boost increases cylinder pressure and therefore stresses the internals more than the stock setup. Knock does the same exact thing, just more abruptly. Knock is more dangerous due to the spike in pressure it creates.

Think of it like an axe chopping a block of wood. Say you swing the axe and it instantly exerts 300 psi of force upon the wood. The wood splits. Take the same axe and gently place it on the wood and then add weight to it to equal that same 300 psi. The wood won't split instantly ... but it will eventually.

 

I am getting ready to turbo my 02 lancer oz and i only plan on running between 5-7 to be safe until i can afford new internals.

 

okay i see the concept...

i take full responsibility on what happens to my motor.
if it blows, my setup in my living room will take over and make more power

 

Like someone else mentioned, some cars run fine on 10 psi. If it's not knocking then it'll run for a while ... maybe a long while. It sounds like you have an eye on it so I'm sure it'll be fine. =)