[Morthoron]

Hmmm...offhand, I would say that Frodo did not spend his time becoming Sauron; on the contrary, he did not possess the will or need to dominate. The Ring, more coersive and addictive than any drug, simply took control of him where it was at the zenith of its power, in Orodruin. The Ring certainly played on the vanities and greed of those that possessed it (Gollum and Isildur, for instance), but what allowed Frodo to almost succeed was that he did not wish to have the Ring, he did not seek power. However, Frodo's spirit had ebbed due to sting and stab (an insidious wound by a Morgul blade that never fully healed), and he could not overcome the Ring's influence. If he had not been injured and fatigued beyond endurance, would he have had the will to complete his task? The idea is at least compelling enough for further consideration. Bilbo gave it up (after bearing it far longer), Bombadil played parlor tricks with it, and Gandalf, Galadriel and Faramir refused it, although each in their own way either coveted it or considered using it against Sauron.

Therefore, the fall of Sauron occurred precisely because Frodo lacked the intent to become Sauron personified, and his mercy and compassion -- virtues utterly alien to the Dark Lord -- compensated for his inevitably succumbing to a power greater than his weakened spirit could handle. In any case, a Hobbit such as Frodo seemed to be the perfect carrier for the Ring because Hobbits, for the most part, did not have societal interests in domination, bellicosity or overweaning greed, being a good-natured, peaceable and simple folk.