The Service Manual states that the tranny will need 11 quarts after a pan drain, 12.6 quarts after an overhaul, and 15.0 quarts if the tranny is dry. Interestingly, my Service Manual (2002) doesn't have the procedure in it, but it was in the 2001 SM. I might just buy the Transmission Unit Repair Manual because the filter change is a bit hazy in the 2001 SM, and nonexistent in mine.
I personally feel like if you drain the pan and change the filter, that's good enough. You'd have changed 11 of the 15 quarts. If you do this every 50,000 (or maybe 30,000) instead of the recommended 100,000, then I personally think it would be ok. I've always followed the recommended time, and always just drained the pan and filter and I've also never had a problem. But I can understand if this isn't for everyone. You can never be too cautious.