What I've always heard is to avoid 'power purge' transmission fluid exchanges like the aamco thing. some fluid in/out exchangers use a single tank with a sort of piston between them so the in/out pressure is similar....those are OK AFAIK
as for the change intervals... they vary between year, model, and mfr as widely as the looks. they can be anywhere from 20k to 100k to "non-serviceable" however that doesn't mean you SHOULD go that long. as for the 'regular' and 'severe duty' conditions, unless you drive 90% highway without towing you most likely qualify for severe duty.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
Tow your vehicle on all four wheels without the need of dollies. No odometer mileage accumulation on vehicles with electronic speedometers. All that from a patented system that a mechanic can install in approximately 6 hours.
Looks like it costs $1000, though, so it wouldn't make sense for EOC. $1000 buys a lot of gas...