Today I ran into the 999 measure limit in GarageBand. The app is built with music in mind, with a default of 120 beats per minute. When I dragged in a couple podcast tracks that clocked in at one hour and 14 minutes, I couldn't hear all the way to the end and my waveforms weren't showing up in the editor. Turns out it was too much information for GarageBand to natively display (despite that I'm on a quad processor desktop with 3Gb of RAM) and you have to turn down the beats per minute to 40. Once you do that, everything will magically work just fine.