I don't know anything about shortening the lifespan of the screen, but I've had my external SyncMaster P2450 overclocked to 75Hz through half a year now. I just love the effect is gives, and together with the Smooth Video Project (SmoothVideo Project (SVP) - motion estimated frame interpolation with any video player and frame doubling in real-time) software, videos look stunning. Using the InterFrame script to make movies like Pacific Rim play in 75FPS makes it look glorious - We seriously need more development on the PC side of things when it comes to displaying movies. DXVA is a step in the right direction though, and it helps keeping the FPS up a lot. One thing I have noticed though, is that the brightness of the screen takes a tiny hit when OC'ed. I don't know if it only affects this particular screen, but it's something to keep in mind.