The Pileus hat article on Wikipedia says that in Ancient Rome, when a slave was freed, there was a ceremony in which his head was shaved and a pileus "was placed upon it".
In the SE question: How did people distinguish slaves from free people in Ancient Rome?, user Tyler Durden addresses this.
My question is: for how long did they have to wear the hat? Until the hair had grown again? Please, tell me it was not for life.