When the opening verses of Surah Al-muzammil was revealed, the Companions would pray as long as they would pray during Ramadan until its last verses were revealed. The period between the revelation of its opening and the last verses was one year.  

لَمَّا نَزَلَتْ أَوَّلُ الْمُزَّمِّلِ كَانُوا يَقُومُونَ نَحْوًا مِنْ قِيَامِهِمْ فِي شَهْرِ رَمَضَانَ حَتَّى نَزَلَ آخِرُهَا وَكَانَ بَيْنَ أَوَّلِهَا وَآخِرِهَا سَنَةٌ  

When the opening verses of Surah Al-muzammil was revealed, the Companions would pray as long as they would pray during Ramadan until its last verses were revealed. The period between the revelation of its opening and the last verses was one year. (Using translation from Abū Dāʾūd 1305)  

لَمَّا نَزَلَتْ أَوَّلُ الْمُزَّمِّلِ كَانُوا يَقُومُونَ نَحْوًا مِنْ قِيَامِهِمْ فِي شَهْرِ رَمَضَانَ حَتَّى نَزَلَ آخِرُهَا قَالَ وَكَانَ بَيْنَ أَوَّلِهَا وَآخِرِهَا نَحْوًا مِنْ سَنَةٍ  

[Machine] "I heard Ibn Abbas say: 'When the first Surah Al-Muzzammil was revealed, their standing (in prayer) was like their standing during Ramadan or similar to their standing during Ramadan, and there was a year between its first and last revelation.'"  

سَمِعْتُ ابْنَ عَبَّاسٍ يَقُولُ «لَمَّا نَزَلَتْ أَوَّلُ الْمُزَّمِّلِ كَانَ قِيَامُهُمْ مِثْلَ قِيَامِهِمْ فِي رَمَضَانَ أَوْ نَحْوَ قِيَامِهِمْ فِي رَمَضَانَ وَكَانَ بَيْنَ أَوَّلِهَا وَآخِرِهَا سَنَةٌ»  

When the opening verses of Surah Al-muzammil was revealed, the Companions would pray as long as they would pray during Ramadan until its last verses were revealed. The period between the revelation of its opening and the last verses was one year. (Using translation from Abū Dāʾūd 1305)   

سَمِعْتُ ابْنَ عَبَّاسٍ يَقُولُ لَمَّا نَزَلَ أَوَّلُ الْمُزَّمِّلِ كَانُوا يَقُومُونَ نَحْوًا مِنْ قِيَامِهِمْ فِي شَهْرِ رَمَضَانَ حَتَّى نَزَلَ آخِرُهَا فَكَانَ بَيْنَ أَوَّلِهَا وَآخِرِهَا قَرِيبٌ مِنْ سَنَةٍ