Peter Jackson, director of the three Lord of the Rings films, is interviewed in the 2004 Wired Rave Awards:
There were two shots of Gollum in Fellowship. We kept him in the shadows — he wasn’t good enough for dialog or a close-up in daylight. We worked on him for another year, and he was in 300 shots in Two Towers. A month before delivery of that film, [visual effects supervisor] Joe Letteri insisted on redoing all of it because we’d finally gotten the code for Gollum right. Even so, after Two Towers, we still weren’t happy with the subtlety of Gollum.
I have to say, Gollum will date those movies in a bad way. If they saved all their motion-capture data, audio, etc. though, they can keep refining those scenes and releasing new editions of the trilogy — year after year after year.