To maintain the stability of the circadian rhythm, all polyphasic sleep schedules must stay relatively consistent day-to-day, without large changes in core or dark period timings. As such, schedules that are not aligned with the 24-hour day are unsustainable and unhealthy. Examples of which includes cycles longer than 24 hours (delaying sleep phases continually) or employing drastically different sleep schedules on a day-to-day basis.
为了保持昼夜节律的稳定性，所有多相睡眠时程的主段或暗期时间都不能有太大的变化，必须每天保持相对的一致性。因此，非24小时周期的时程是不可持续的，更是不健康的。这方面的例子包括周期超过24小时（不断推迟睡眠阶段），或是每天采用完全不同的睡眠时程。
