If you want to extract the absolute maximum life from your transmission, I'd perform a flush every 50-60K miles, and not wait for 100K.2011 FJ here. I started getting the shudder at just under 139k miles. After reading the MANY threads in this issue here, I went to the dealer for a complete flush (not a drain and fill). The tranny has settled back down about 95% with 2k miles after the flush, and I'm hoping for a little more. In any case, much improved and no shifting ossues. I wish Toyota would just say how often this should be done as routine maintenance, and not just for extreme driving conditions. I'll be doing it every 100k from now on (fingers crossed to make it that far).
There isn't a fine particulate filter in this transmission, and all the clutch wear debris just circulates perpetually, wearing out O-rings and seals in the valve body. The less debris there is suspended in the ATF, the slower all the soft seals wear.