Toyota shot themselves in the foot by marketing the sealed transmissions as having “lifetime fluid”. Fluid analysis has indicated that the cooling properties of the World Standard ATF break down after around 40,000 miles. They are banking on the fact that Aisin transmissions used in Toyota’s (still reliable overall, but comparatively the least reliable aspect of the powertrain) will in most cases outlive the cars themselves before they are written off as totaled by an insurance company or salvage titled over the years.

The Toyota maintenance schedule doesn’t mention transmission servicing at all on most of their vehicles. However, the Lexus maintenance schedules recommend a fluid flush at 120k miles in the severe schedule for some of their cars with an identical engine/transmission (e.g. Lexus ES vs Camry). Meanwhile, both Lexus and Toyota dealerships will happily sell you a transmission flush regardless of the maintenance schedule. I’ve learned nobody really knows what’s best since they’ve omitted key maintenance info for marketing/metric purposes, so you’re best off flushing every 100k miles at most.