The ruling on standing in night prayer with eight rak'ahs and a single taslim

Question:
May Allah reward you, Honorable Shaykh. This questioner says: Is it valid for me to stand in night prayer with eight rak'ahs and a single taslim, since for years I have been doing this and I have become accustomed to it?

Answer:
I heard that the Messenger (peace and blessings be upon him) would recite the eight rak'ahs in succession, sit after the eighth without saying the taslim, then stand up and perform the ninth, recite the tashahhud, and say the taslim. If you do this, then it is a form of the Sunnah of the Messenger (peace and blessings be upon him). However, it is not befitting to make this a constant habit. The Messenger (peace and blessings be upon him) would do this at times and do this other way at other times. Yes.