Wa alaykum salam wa rahmatuLlahi wa barakatuHu,

The minimum number of tasbih’s is one. The least number requested for a perfect tasbih is three. (Tuhfat al-Muhtaj v. 1, p. 199) And it is permissible to end the prayer with taslim immediately after reciting prayers on the Prophet Muhammad and his family. (Ibid)

The time it takes to make three tasbih’s is very little, maybe like an extra twenty to twenty-four seconds. The reward that one will receive for perfecting the salah is worth taking the extra time. Thus, one should try to at least say it thrice. Perhaps, one could try to prepare for the salah before the time enters, by making wudu, etc., then more time can be spent in prayer.

And Allah knows best.