Both of the Toyotas I've owned haven't had their ATF changed and it hasn't been an issue. I have my doubts I'm that lucky.
One was a 2005 V8 4Runner I sold with 255k miles and my current truck is a 2010 Tundra that just rolled 203k miles.
The 4Runner towed and went offroad a lot and the Tundra does a whole lot of towing. No hiccups to speak of in either vehicle.
With regards to changing the fluid, most vehicles have a trans cooler and the soft lines can be removed in order to perform the fluid exchange...the flow-out side of the soft line goes into an empty bucket and the flow-in side goes into a bucket filled with the correct ATF for the vehicle. The hydraulic pump in the transmission does the rest. No special tools required. Not saying there aren't special tools or procedures, just saying there will be a pair of soft lines on the vehicles equipped with trans coolers where the fluid exchange can be performed.
If anyone is really that nervous about changing out all the fluid at once, small amounts can be introduced in a few intervals (say, every 2000 miles or so) until the entire system has been exchanged.
Additionally, in the newer vehicles there can be sensor failures that give the impression the trans has failed or is failing. This is where you want to have someone look at the Transmission Control Unit (TCU) to see if there are error codes as those codes can exist within the TCU but not necessarily show up as a Check Engine Light (CEL).
IMO, if you're changing ATF and something fails, there was an issue prior to the fluid change.
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