For what it's worth:
A GeForce 6800 GS performs virtually identical in every single benchmark to a GeForce 6800 GT. But it costs $100 less. The reason? The GT is the postfix used for the hardcore gamer. Instead of moving the 6800 GT down the line to the "value/performance" category (and soiling the "GT" name, as if these postfixes actually mean something to someone), they came up with another postfix, the GS, and called the card a 6800 GS. Instead of dropping the price on the 6800 GT, nVidia is just stopping production and letting the rest sell at $100 more than the 6800 GS, which has nearly identical performance.
The 6800GS is cheaper and cooler than a GT lowering the cost to manufacture due to the 110 nm process (GT is 130 nm) which yields many more chips per wafer. BUT nvidia is headed to 90 nm which will be cheaper still.
Product life cycle? Probably 18 months at best. The 7800 is also a 110 nm process so when the 90nm stuff comes ouit the 6xxx line is history.
They just aren't keeping the old lines running due to cost. New chips are smaller which means faster and cheaper so there is no demand for the old ones unless they have a cult following. Also, the scum sucking bastards are not dropping the prices on old chip lines, they are just discontinuing them since the newer, faster chips are also cheaper to make.
Why do you ask? If you buy from a reputable board maker and yours dies in warantee, but after the line is discontinued, just insist on a replacement with a next generation chip of comparable (or better) performance. They usually give in pretty quick on the $200 plus cards.
