Making up naafil acts of worship
Question

                When do we say that naafil acts of worship should not be made up? Is it because it is a Sunnah for which the time or place is no longer applicable? We know that the Prophet (peace and blessings of Allaah be upon him) used to make up some naafil acts of worship when the time for them had passed, such as Witr.
Praise be to Allah.Naafil 
          acts which are done for a specific reason should not be made up once 
          the reason is no longer present. For example, if the sun is eclipsed 
          and a person was asleep, then when he wakes up he finds out that there 
          has been an eclipse, he should not do the eclipse prayer because the 
          occasion has passed. Similarly, if a man enters the mosque and stays 
          there for a long time thinking that he does not have wudoo’, then he 
          remembers that he does have wudoo’, he should not pray Tahiyyat 
          al-Masjid (two rak’ahs to “greet the mosque” upon entering) 
          because it is a Sunnah and the occasion for it has passed. The guideline 
          in these cases is that every naafil act which is done for a reason should 
          not be made up later, such as Witr. The Prophet  
          (peace and blessings of Allaah be upon him) did not make up Witr as 
          such; he would pray twelve rak’ahs of Duhaa (optional mid-morning prayer). 
          The most he ever prayed in Witr was eleven rak’ahs, so he made up the 
          most but he made it even, because the occasion for praying Witr had 
          passed.