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.
為了保持晝夜節律的穩定性，所有多相睡眠時程的主段或暗期時間都不能有太大的變化，必須每天保持相對的一致性。因此，非24小時週期的時程是不可持續的，更是不健康的。這方面的例子包括週期超過24小時（不斷推遲睡眠階段），或是每天採用完全不同的睡眠時程。
