I first noticed a strand of grey hair when I turned 20. As I progressed through my 20s, that single strand gained siblings - lots of them. I started dyeing my hair at 30 and have been dyeing it ever since. In between colouring sessions, I notice my roots are salt and pepper - there is still a lot of natural black in there but yes, there is also a lot of grey. I would say that my natural hair is much like the woman's hair in the first photo below.
A part of me thinks I am still too young to go au natural, especially as I live in a youth-obsessed culture and work/worked in a youth-obsessed industry. But then I see photos like these and it makes me think. These women are stunning, aren't they. And they've kept their long, lustrous hair. Hmmm, much to ponder on.