There is no requirement to reboot the line modules on a regular basis in a TA-500X chassis. I would only drop your customers and perform a reboot if there is a global issue common to all customers on that module.
We have several TA5000 in service. No need to reboot the card unless upgrading firmware. Sometimes if the CPE gets wedged on a specific DSL interface, doing a shut/no-shut on that specific interface will restore service to that customer. Usually a power-cycle of the CPE will fix it.