I'm soon 39 with maybe 20-30% grey. I've dyed it at home for some years, at sporadic intervals, but it was such a mess and a hassle, I felt. Once I could afford to get it done professionally I was so pleased with the results and the compliments that I deicded to treat myself to it 4 times a year. That way it still grows out and I'm reminded what I really look like
but I get to feel real pretty at regular intervals 
I'd prefer to have the grey show, but not just as a "helmet". I'm working on it - next time I'll try having it cut shorter and having greyish stripes.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett