Common usage today is 20 years. The time from the birth of a child until that child births the next generation.
But I prefer the old usage which is the biblical usage which is the life span of a man; three score and ten or seventy years.
So, for something to be a tradition it would need to be practiced a minimum of 140 years.
So, when Paul the Apostle referred to “traditions” received from Paul in 2 Thessalonians 3:6, where they 140 years old, or a much shorter period of time?