Recording more than 2 USB mics on Mac

I was able to add two Rode Podcaster usb mics as an aggregate device (Applications > Audio MIDI Setup) and then stereo record them in Audition. It works great. However, now we need to add another USB mic to the mix. (3 mics in total)

Is this still possible via the Aggregate Device approach, or, are there limitations? I just don't want to buy another RODE mic if it doesn't work.