Black,
What I ended up doing is kind of nifty. I wanted to have permanent storage as well, but I did not want my card to stick out so far as I catch it on things in my travel bag. I found a shortened Micro SD adapter for $8.00 and put a very fast Transcend 64GB Micro SD
card in it. This thing only sticks out of my Air 1/8th of an inch. See below and thanks for the advice!
I did some benchmarking tests on the drive after I got it and found that leaving the card as exFat was a bad idea because of file size limits and the fact that movies can end up being pretty large. I ended up doing exactly as you suggested and have had great results.