I re-sharpen my hooks anytime I catch a fish, bump a rock or drag the bottom (and yeah, in some cases that's pretty frequent!).

I use the Gami and Vision Siwash's, and they seem to resharpen well IF you keep them sharp. Let them go bad and your swapping hooks.

Hooks are changed out when I don't feel that the hook can hold the super sharp point needed to drive that point into the mouth of a fish. Driving a 1/0 or 2/0 "home" is not always easy, and it also helps to use a rod with sufficient backbone to drive that hook home. I pinch all barbs, as having to drive that barb in (legal or not) makes it all the more difficult to get a hook-set and causes much more damage to the fish being released.

Mike