‘Rejoice always, pray without ceasing, give thanks in all circumstances; for this is the will of God in Christ Jesus for you.’ (1 Thess 5:16-18).
During my last medical check-up, the cardiologist put me through a treadmill test. He asked me to keep moving until he stopped the machine. For some reason, I pressed the stop button after a while since I felt uncomfortable. Probably, I was wearing the wrong shoe on that day.
The exhortation to pray without ceasing is to keep praying for something until we receive the signal to stop. This is important because most of us give up before our prayers reach their proper end.
Why do people give up prayers? There could be various reasons. Discouragement is the main reason. We keep praying and there seems to be no result for a long time so we drop praying. This is tied to a person's level of patience because discouragement sets in for different people at different periods. Some, with longer patience may go on for longer periods because they surrender to discouragement slower than others.
Praying for the wrong thing also bring discouragement. God will answer our prayers according to his will. Prayers for wrong things are not going to be answered. Since such lives are dotted with unanswered prayers, they lose the steam to advance in their prayer-life further. Thus ceasing such prayers are not bad but will do immense good to our spiritual life.
When is the right time to stop? The simple answer is to stop when the prayer is answered. But what about prayers that will never have an immediate answer or could be open-ended. For example, praying for the welfare and peace in my country is an ongoing prayer. It doesn't seem to happen in the near future though I would like to see it happen in my life-time.
Prayers without end in sight are prayers that shape us spiritually. Such prayers draw us regularly to the bossom of the father. Such prayers keep us prayerful. Finding such things to pray helps us to pray without ceasing.