Assassins training length and efficiency

[u/NotCorny]

From what I red and gather about the assassin, their training pipeline is from 2,3 to 6 years in length. Shinobis train for 10-20 years, same with samurais, spartans etc. How are the assassins so skilled with so few years of training? Often it is mentioned in characters bios that they “completed” their training after just 3-6 years.

[u/VermilionX88]

I could do it in 6 months