ATF Drain and Fill

[DMZ]

My ,05 Yaris has 71k normal driving miles on it.

I noticed recently that it was shifting with just a very slight jerk.

Looking at the ATF color, showed it to be reddish brown, so I did a drain and fill.

When I looked in the drain pan I could see the the old ATF was a bit "muddy" in color, but the big indicator was the smell. I had a fairly funky smell to it.

2.6 qts of fresh ATF made a difference in the shifting. It is back to it's normal barely perceptible smoothness.

I know the CW is that Toyota WS last the life of the car, but I can't help but wonder what the old ATF would look and smell like at say 120k or greater and would it still be providing proper lubrication?