"The early years are the most important period of children's lives."

This is a significant period of his life, from age 15 to 35.

We know less about this period of his life than any other.

I think that this was the most happy period of my life.

He later described this period of his life as very difficult.

For Laura, and her girls, during the most difficult period of their lives?

"Unless the word was associated with a specific period of their lives, such as military service."

He described this time as "the most trying economic period of my life."

I wanted to give him something he could identify with, from a very positive period of his life.

Well, that depends on what period of her life you're talking about.