I'm 47. I have a lot of grey on the underside of my head and what I consider to be a cool white streak right up front where I part my hair. It started when I was about 40. My mom did the 'frosted' look from the mid-70s until recently (she's 73) so I have no idea when she actually went mostly grey.
I'm pro natural look. I'm way too lazy (and cheap) to do the work of coloring my hair with any regularity. Did it for the hell of it in my 20s and know I cannot manage to keep up with it.