Instagram tests new update for Stories

Now Instagram stories will have frame count displayed along the bottom of the screen, indicating that users can swipe left to see more — and perhaps Instagram believes that having too many frames will be off-putting, diverting users away from the vertical swiping experience.

Perhaps it's a technical limitation, and Instagram can't get it to operate past a particular frame count. If it is implemented, you may expect your Stories performance to suffer, particularly in the later frames, which few people will manually tap through to see.