I disagree with your assessment. To an average user, whatever winds up saved in their browser cache is there mostly unintentionally. Yes, it's saving info from sites they choose to visit, but after that initial choice, the user is out of the loop. The browser saves what it needs to without user notification or input. I might even wager that most users are unaware of their browser cache, or don't know what's in it or how to access it. Therefore, I believe your metaphor perhaps confers too active a decision-making process on something that most people are completely unconscious of.

To be clear, the strawman average user I'm using here is me. I know I have a browser cache, I know vaguely what is stored in it and why, and I know how to clear it if I'm having certain issues. That's about it. I sure as heck don't treat it as an archive.