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human
[LOTR] Why doesn't Gollum age after loosing the ring?

Gollum hardly ages when he has the ring. Ok, same with Bilbo. But when Bilbo leaves the ring he quite quickly turns into a hobbit-raisin hybrid. Why then, when Gollum was once a similar creature to a hobbit, doesn't he age after Bilbo takes the ring from him?
gpt
We don't know for certain that he doesn't age after losing the ring.

Smeagol was a proto-hobbit and hobbits tend to have relatively long life spans.

Additionally, he got the ring when he was fairly young, being about 33 at the time (born circa 2430 third age, got ring circa 2463 third age.)

The time between he lost the ring and he died was 78 years, which means he was biologically around 111 at the time of his death, which is fairly old but not outside the realm of possibility for a hobbit.  This is assuming that he stopped biological aging once gaining the ring.

What's interesting about that age is that Bilbo gave up the ring at 111 years of age and Smeagol permanently 'gave' up the ring at that biological age as well, when he fell into Mount Doom with the ring on his person.