Throwout Bearing Failure

[blazing hatch]

I just took my 11 yaris hatch in to have the throwout bearing replaced, thankfully under warranty. It's current mileage is only 21,000. So it has me alittle concerned about this being a continual thing. By the way this is not my first vehicle with a manual trans. Been driving a stick for years, and this is my first brand new car. I've replaced clutches before but never just for the throwout bearing.
I was wondering how many of you guy with manual trans Yaris, have had to replace the T.O. bearing? and at what mileage interval? My wife's 07 sedan with auto trans has 50,000 miles, and has needed nothing other then it's normal 5,000 mile servicing and tires. Thinking I should have bought and automatic trans now.