The 'film camera' metaphor is how I have always imagined it works as well. It makes sense from an evolutionary standpoint. It's critical that you are able to retain knowledge in your 'formative' years. But after a certain point it less important to record new information. I have always wondered if the amount of info we store drops off proportionally or exponentially.

Consequently, when someone has a bunch of adrenaline dumped into their body, they often say that time 'slowed down.' I believe this is further evidence that our brain boosts the bit rate on our memories at critical moments.