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