I just replaced mine at 24k. It started squeaking intermittently. I got a goodyear gatorback for like $30. Here in vegas they didnt carry any belts for the titan at autozone but they had it at checker.
i agree..if in doubt, just change it. i had to change mine because it wasnt entirely on the pulley and frayed one side. did it myself. would have been easy if i had a longer breaker bar when putting the belt back on. just removed the rad hose and i was good to go.