2001 Toyota Camry Frequency of Transmission flush

Is there a recommendation from the factory? I would think it would also have to do with what driving you do. To be safe, 50k miles would seem reasonable as most car makers seem to be into the "lifetime fill" these days. I am not sure what lifetime the reference is, but 50k is a reasonable amount of mileage, you don't need to change it too often, however neglecting this maintenance can be harmful to any car.