Crucifixion of Christ 30- 33 A.D.
 
Wicked generation  judged 40 years later = 70 A.D. When th Romans destroyed Jerusalem.
 
When the last vestige of Jewish resistance was wiped out at Masada in A.D 73=75 the destruction of Jesus generation was complete.   Historians tell us that Jesus Christ was born around 4 B.C..  Assuming that the generation that Christ had described had expired by 75 A.D. the length of that generation would be between 70 and 80 years.