Is it teenage years?

是青少年时期吗？

During our teenage years, tanning was all the rage.

在我们十几岁的时候，人人都疯狂的去美黑。

Let it remain forever, gloriously, in my teenage years.

还是让它永远辉煌地，珍藏在那里，珍藏在我的孩童岁月里。

I had always a problematic skin since my teenage years.

我自从青少年以来，就一直是属于问题肌肤。

It usually occurs before the age of 40, often during teenage years.

这种情况通常在40岁之前发生，在青少年时期。