Bilbo aged noticeably after parting with the ring. Gollum had it for something like 500 years? You'd think he'd instantly turn into dust after losing it. As far as I can tell, there's no difference in his appearance at all in The Hobbit to when he appears in LOTR.
The Hobbit: An Unexpected Journey (2012)
If Bilbo aged post-ring, Why didn't Gollum?