V modded 9800 Pro, would it allow much more overclock

Right now with my modded VGA Silencer (see sig) i'm at a stable, artifact free 450/380. With the VGA Mod, I really don't think cooling is a problem (74CFM and I still may double that!)

With a voltmod would it go to around 500/400?

Would it signifigantly reduce the life of the card (still needs to last atleast a year at these settings)?

I'm considering the voltmod since i've hit the max overclock without artifacts I can, and a voltmod is the only option left to get to 500/400 which would be my goal. Should give 24000+ 3D01, 7000+ 3D03 and 52000+ AM3 (current scores at 2.5ghz are in my sig)

If you have r360 core you can flash to xt, so far I did on my 9800 vdimm mod for memory still can't get to 400 without artifacts, I heard that if you do gpu volt mod you can go from 450 to 480 but can't confirm it,

Well, voltmodding and overclockng aggressively will eventually kill your card. It might take 2 months, it might take 2 years. If it needs to last a while I wouldn't Vmod it.

Aswell, no clocks are a sure thing, it might increase 5 mhz, it might increase 50 mhz.