It is said: The season for learning runs from the cradle to the grave.
تعليم المتعلمal-Zarnūjīفِي وَقْتِ التَّحْصِيلِ
On the Times Best Suited to Acquiring Knowledge
Ḥasan ibn Ziyād began serious fiqh study at eighty, spent forty years not sleeping on a soft bed, then issued fatwā for another forty years.
Best times are the bloom of youth, the pre-dawn hours, and the span between the two night prayers. Devote all your hours: when one subject wearies you, turn to another.
وَكَانَ ابْنُ عَبَّاسٍ رَضِيَ اللهُ عَنْهُ إذَا مَلَّ مِنَ الْكَلَامِ يَقُولُ: هَاتُوا دِيْوَانَ الشُّعَرَاءِ.
When Ibn ʿAbbās, may Allah be pleased with him, wearied of discourse, he would say: Bring the poets' diwān.
وَكَانَ مُحَمَّدُ بْنُ الْحَسَنِ لَا يَنَامُ اللَّيْلَ، وَكَانَ يَضَعُ عِنْدَهُ الدَّفَاتِرَ، وَكَانَ إذَا مَلَّ مِنْ نَوْعٍ يَنْظُرُ فِي نَوْعٍ آخَرَ، وَكَانَ يَضَعُ عِنْدَهُ الْمَاءَ، وَيَزِيلُ نَوْمَهُ بِالْمَاءِ، وَكَانَ يَقُولُ: إنَّ النَّوْمَ مِنَ الْحَرَارَةِ.
Muḥammad ibn al-Ḥasan would not sleep at night; notebooks lay at hand — when one subject wearied him he shifted to another. He kept water nearby, banished sleep by splashing water, and would say sleep comes from heat (in the temperament).