[Richard L]

Continuous operation is limited by temperature rise of the motor winding. Since there is no effective way to cooling them whilst they are rotating, the rate of temperature rise is affected by the ambient temperature.

In order to extend the continuous running period, you can reduce the running current by reducing the bypass pressure and RPM. 50% DC is one way to reduce dissipation in standby mode.

If you do have "standby" period, then it is not continuous but regarded as intermittent duty.