The Messenger of Allah ﷺ used to pray standing at night for a long time, and used to pray sitting at night for a long time. When he prayed standing, he bowed standing, and when he prayed sitting, he bowed sitting. (Using translation from Abū Dāʾūd 955)
كَانَ رَسُولُ اللهِ ﷺ إِذَا صَلَّى قَائِمًا رَكَعَ قَائِمًا وَإِذَا صَلَّى قَاعِدًا رَكَعَ قَاعِدًا