I was watching how they made "Van Helsing" (1997) at ILM and it appeared they key-framed every frame.  plus it almost looked like they were using P2 figures for animatics to send to crew shooting in prague.   like 2000 hrs per day of rendering the final shots.  they didn't say if they hired that out to korea at $2 per man-hour and made them do the tweeners, in which case there woulda been alot less keyframes sent out.

for ordinary poser anim, they'll tell ya to keyframe every 15 or 30, which is good enuff for this stuff.