How does TC/TM prioritize backups and deletions?

Question

I've recently installed a 500 GB TC and have used it to set up a backup schedule for two Macs using TM. I also want to add some archival files (old and unchanging, currently stored on several external HDs) and at a point in the near future I will want to back up a third Mac which isn't available at this point. My questions:
* Does TM delete old files on its own when it gets full to make room for new ones? If so, how would you run out of disk space as this support article http://docs.info.apple.com/article.html?path=Mac/10.5/en/15137.html suggests?
* Can I override TM's logic by directly backing up my archival files onto my TC hard drive? (In other words, I assume if I connect my archival files to my Mac and backup through Time Machine it will see these as part of my Mac at a point in time and will eventually delete these files, but if I simply use the TM as a hard drive would they be protected?)
* Suppose I do run out of space and decide to delete some backups manually? Can I simply delete the oldest ones first? As a new user this looks like a risky practice because my first backup consumed much more space than any of the subsequent ones, which makes sense because those were just backing up changes.

Answer 1

So I guess I would have to manually delete the oldest backups from the sparseimage for the first Mac, to gain space for backing up the second Mac?
Some kind of preference setting for this would be welcome. If I start backing up two Macs, and continue to do so, then will they just compete about the space until full, will they occupy space 50/50 or dependent on how often backups are done?
Very strange that Apple does not explain how backing up several Macs actually works. I have posted feedback to Apple on this.