So, my personal opinion is to not sweat it. There are several factors that contribute to belts breaking down. Time, use and temperature.
I lived in San Antonio and I know the weather. Dry but hot in summer, nice in the winter. That belt is fine. You don't have the extreme temperature weather swings you get in the Northeast. Snow, then heat.. cold. That constant cycle will help kill a belt.
It should be done at 90k, but that is with a large margin of error. I talked to a toyota guy who said they see them coming in all the time at 110, 120k.
So, what I am saying is I personally bet your belt is fine. Austin temperature/weather is very easy on cars. I had a San Antonio Truck that was 10 years old and looked brand new underneath.
Give it 10k, 20k then get it changed.
If, however, you are uneasy. Have them do it. 1200k is a small price if it makes you feel secure, but having first hand experience on how nice that climate treats cars, I would not worry.