A few random videos I pulled from youtube had a key frame on average every 4.5 seconds, ranging from 0.1 to 5.5 seconds apart, seems pretty consistent regardless of type of video, at least for the few I tried.
The worst I've seen in production was a poorly configured encoder that insert a keyframe exactly every 30 seconds, along with segments every 10 seconds, which surprisingly, caused some players to crash trying to find a keyframe.
The worst I've seen in production was a poorly configured encoder that insert a keyframe exactly every 30 seconds, along with segments every 10 seconds, which surprisingly, caused some players to crash trying to find a keyframe.