Are grace age believers required to have a set time or hour for prayer?
No. Grace Age believers are not stipulated to any particular hour for prayer or required to meet at the church house at a set time. That kind of fixed prayer hour belonged to the Jewish ritual, such as going to the temple at the ninth hour, and is also practiced by Mohammedans.
Les explains that nothing in church doctrine stipulates a particular hour when believers must go to prayer or meet at the church house for prayer. He contrasts grace age believers with the men in the passage, who were still under the Jewish habit or ritual of going up to the temple at the ninth hour because it was the hour of prayer. He also notes that Mohammedans have their hours of prayer throughout the day. For grace age believers, however, no such fixed hour is required.