[Plugin: WP Super Cache] Questions about how super cache works

Please forgive me if these are stupid questions, but I’ve read through all the documentation, scanned the code quickly (keep in mind I’m not familiar with WordPress code though), and read through the comments. I was wondering if someone could help answer a few questions:

1. Does an update to a post or page immediately invalidate and update the cache for that post/page?
2. Does a comment on a post immediately invalidate and update the cache for that post?
3. Can you clean out aged cache items by running a cron job? (i.e. a cron job executed by the system that could run until it was finished). I’m assuming that otherwise super cache clears the cache by checking it on every request which I would think could slow down users seeing dynamic content. Plus, if a lot of users just hit the cached page, the cache could end up aging tremendously until a “dynamic” user requested enough pages to get the cache cleaned.

Any help here would be appreciated. If I seem anal, I’m a programmer by trade and always like to know how things work :^).