I say: the sounder view is that performing the tashahhud in every single rakʿah is impermissible; Allah knows best. If, at the outset, a person intends a fixed number of rakʿahs, he may later increase or decrease that number on condition that he changes his intention before performing the additional or omitted units; otherwise, the prayer is invalid. Thus, if he intended two rakʿahs but—through forgetfulness—rose for a third, the preponderant opinion is that he should sit back down, and may then, if he wishes, stand again to add further rakʿahs.

I say: night-time voluntary prayer is superior, with the middle portion of the night being the most virtuous, followed by its last portion. One should conclude with the salām after every two rakʿahs, and the tahajjud is recommended. It is disliked to spend the entire night in prayer habitually, to single out the night preceding Friday for a special vigil, or to abandon a tahajjud practice to which one has become accustomed. Allah knows best.