[geoschmo]

First of all, the ring had unatturally extended Gollums life. This may not have been made clear in the movies, but it was a key point in the books. It had the same affect on Bilbo, to a somewhat lesser degree. The books made a big point about the fact that Bilbo, while having not quite reached an age unheard of for Hobbits, certainly was not showing the effects of his age that you would expect. Once he gave the Ring to Frodo, his age started to "catch up to him", as could be seen at Rivendell. And once the ring was destroyed he began to age very fast. Compare his appearance at the begining of the FOTR with the end of ROTK. He appears to have aged decades in a span of less then two years.

Smeagol was of a race of creatures not very unlike Hobbits. And yet he had outlived his expected lifespan by who knows how long. Perhaps a century or two. Once the ring were destroyed he would have faded away very quickly indeed considering how much longer it had extended his life.

Secondly, Gollum was not totally free of the power of the ring at the end. He wasn't trying to get the ring away from Frodo to save Frodo. He wanted the ring for himself. In the struggle he fell into the pit with the ring, destroying both of them in the process. But saving Gollum would have meant that he didn't fall. And if he didn't fall he wouldn't have thrown the ring in, so the ring would have never been destroyed.

That was the point in the end. That no one had the strength to destroy the ring. Absolute power corrupts absolutly. But just as in real life in the effort to posess something, we often end up destroying it. The only way the ring could be destroyed was indirectly through the effort to posess it. In effect, the ring was destroyed by itself, because only the ring was strong enough to do so.

Gollum would not have had the power to throw the ring into the pit. The only other way that it could have ended, and the ring still be destroyed, would be for the ring to fall in the struggle but neither Gollum of Frodo to fall. But then Gollum would have been overcome by his desire to get the ring and would have jumped in after it regardless of the danger to himself. Frodo almost did that, you could see it on his face. And he was only under a fraction of the rings control that Gollum had been.