When did the Sunnah become an Islamic knowledge source?

The Sunnah of the Prophet Muhammad (PBUH) has always been the second most important Islamic knowledge source as Allah commanded all Muslims to return to the Prophet for both explanation of the Quran as well as an example for all of mankind. As a result, his Sunnah was collected and followed during his entire tenure of prophethood, from 610-632 ce. 

It was collected from him directly, by his Sahaabas, or companions, who were righteous, focused and very astute individuals in this regard. As a result, most of the Sunnah was related by many authentic chains tracing back to these companions. Furthermore, they were able to relay not just his words, but also his characteristics, moral ethics, interactions and reactions to given predicaments. 

They also relayed his social interactions with friends, strangers, and delegations. The Prophet's homelife and  interactions with family members, blood relatives and in-laws are all accurately recorded. Even the exact gestures and reactions that they witnessed from the Prophet (PBUH) are all compiled within the Sunnah.