Are the recitations of Surat Al-A'la and Al-Kafirun in the Sunnah (voluntary prayer) of Isha, as well as Surat As-Sajdah and Al-Insan in the Fajr prayer on Friday, among the emphasized Sunnahs that should be maintained?

It is recommended to recite Surat Al-A'la and Al-Kafirun in the first two rak'ahs of the three rak'ahs of Witr prayer, and to add Surat Al-Ikhlas and the two Mu'awwidhatayn in the third. As for the sunnah prayer of Isha, there is no established specification of two particular surahs to be recited therein. The sunnah of reciting Surat As-Sajdah and Al-Insan in the Fajr prayer on Friday is established, but the Imam should not constantly recite them for fear that the common folk might believe them to be obligatory.