When does the time for the non-regular, post-prayer Sunnah end?

The post-prayer supererogatory Sunnah that is not ratibah (regularly observed) is called by some scholars "the ratibah that is not emphasized." Its time is dependent on the obligatory prayer to which it is related. For example, the time for praying four rak'ahs after Dhuhr expires when the time for Dhuhr expires.

Voluntary (nawafil) prayers are of two types. Some do not have a prescribed congregational prayer, such as the ratibah prayers that accompany the obligatory prayers. The emphasized ones among these are: two rak'ahs before Fajr, two rak'ahs before Dhuhr, two rak'ahs after it, two rak'ahs after Maghrib, two rak'ahs after Ishaa, and Witr.

The non-emphasized ones include: an additional two rak'ahs before Dhuhr and two after it, four before Asr, two light rak'ahs before Maghrib, and two rak'ahs before Ishaa.

The time for the ratibah prayers begins with the entry of the time for the obligatory prayer, both before and after it, and their time expires with the exit of the time for the obligatory prayer. Thus, performing the pre-prayer Sunnah after the obligatory prayer is considered a timely performance (adaa').