Nasai

1642. Commentary: "Prayed the whole night" — It has been mentioned above that during the last ten days of Ramadan, he (sallallahu alayhi wa sallam) would spend the entire night in prayer. Thus, this narration pertains to the months and days other than the last ten days, so there is no contradiction between them, because the general practice was that he would both sleep and pray. Even in the last ten days, it is possible that he (sallallahu alayhi wa sallam) slept a little, and the majority of the night has been referred to as the whole night. And Allah knows best.

The correct method and the Sunnah are precisely this, because along with worship, it is also necessary to take care of one’s body and other responsibilities. Strict adherence to the obligatory acts (fara’id), ease and enthusiasm in voluntary acts (nawafil), and consideration for other obligations—this alone is the correct religion. Moderation in voluntary worship is extremely important. Allah, the Exalted, has also maintained moderation in the obligatory acts. Extremism is harmful.

Benefit:
One should avoid completing the entire Qur’an in one or two nights.
The practice of “Shabina” (completing the Qur’an in a single night) that is prevalent among memorizers (huffaz) is also something that ought to be abandoned.
However, if the Qur’an is completed in three nights,
then its permissibility may be possible.
And Allah knows best.