Why wasn't Gollum turned into a wraith?

[CAB]

Is the reason Gollum didn’t become a wraith after possessing the Ring for nearly five hundred years explained solely by the Hobbits’ natural resistance, or is there something more?

I think one important point to consider is Gollum’s appearance compared to other mortal ringbearers. Bilbo and Frodo seem simply to be ageing very slowly. We don’t have much of a description of what the Nazgul looked like, but what we do have suggests that they appeared to essentially resemble very old men. While admittedly in one scene (The Stairs of Cirith Ungol - The Two Towers) Gollum is said to basically resemble an old Hobbit, this is the exception. More often Gollum is described in terms more similar to descriptions of Orcs than Hobbits or Men. (Actually I think Gollum may have been essentially been an Orc made from a Hobbit specimen by the time of the Lord of the Rings. No, I am not suggesting that Morgoth or Sauron used rings to make Orcs. Rather I think the twisting and cruelty of the process and the end result were much the same.)

One might argue that the One Ring wasn’t intended to create wraiths since Sauron never planned on another holding it. Yet it seems the evil power of the One and Nine are very similar, probably due to their connection. Why would the One give the holder a view into the Unseen world? Surely Sauron already possessed this power. Why would the One extend it’s holder’s life? Sauron was immortal. I am not sure how the Seven and Three fit in here. My guess is that the Seven at least were basically (if not exactly) the same as the Nine and that the Dwarves simply reacted to them differently than Men or Hobbits would. The Three may have been the exception due to the fact they remained “unsullied” or perhaps their holders reaction was different due to the Elves immortality and strength.

I personally don’t believe that Sauron originally intended for any of the rings to make their holders wraiths. It would make sense that the rings were meant to bring groups of people, rather than only individuals, under Sauron’s control, and so were given to leaders or potential leaders. Why would Sauron want these leaders, who presumably would be coaxing or forcing their followers to serve Sauron, to become wraiths?

My guess is that, in spite of Sauron’s intentions, mortals, or at least Men (and Hobbits are, I believe, a branch of Men) began to age rapidly at a certain point after holding a great ring. Perhaps at this point Sauron must act, probably via the One Ring, creating the “fading” process to cause the ringholder to become a Ringwraith and thus somewhat salvage and retain his servant. If he doesn’t act then the ringholder is relatively quickly twisted into an Orclike/Gollumlike creature. If this were true it would help explain the nature of Gollum’s existence. Obviously, Sauron couldn’t change Gollum to a Ringwraith via the One since Gollum was holding it.
I have no doubt that this theory has some flaws. There is certainly a lot of conjecture in my conclusion. However the original question seems quite intriguing and doesn’t seem to have been discussed here before. I would be very interested to hear what others think about it.