How is the daily rate defined. My definition of a day is 8 hours. So $1500/day = 187.5$/h. So if you work 12 hours a day, do you charge $1500, $2250 or simply refuse to work more than 8h?
If you're charging day rates, you're charging enough to not sweat the small stuff. My standard language is "Such hours as are standard and customary at $CLIENT." I've never had anyone abuse it.