"By default, Aperture's library is confined to a single volume. Consequently, when that volume fills up, you can't add any more images to your library," writes Ben Long on his Complete Digital Photography site. "However, using a little Unix trickery, it's possible to span the Aperture library across multiple volumes to extend your storage. The Aperture Library Spanner is a simple app that will automatically span your library across multiple volumes."
Here's a little background on this nifty tool that Ben is offering for free. We were hanging out in San Francisco on St. Patrick's Day talking about photography over beers. In passing, and quite innocently, Ben mentioned how to span Aperture volumes by setting up a few commands in the Terminal app. I said that a lot of people would use this if it had a nice user interface. Ben replied, "I could do that!" And he did. This is one of the reasons I'm such a strong advocate of photo buddies. By having someone to kick around ideas with, you'll explore things that you might not have considered otherwise.
Thanks to Ben putting together the Aperture Library Spanner, we have two techniques for coping with large libraries. I posted a piece on How to Manage a Large Aperture Library on a PowerBook and Ben's Aperture Library Spanner. In other words... shoot as many pictures as you want!