Yes, the looking young/old can work both ways. I have always looked young for my age, which was a pain when I was, well, young. When I sent my resume out for my internship in the winter, I left off my experience in Arizona and my first job in MA, although it stated I had held various other positions, info available upon request. I also left off my graduation years. No one questioned me; it was obvious I was very experienced, but it looks like I worked for about 16 years and perhaps I had stayed home with the kids for a while. I was definitely older than every single person that interviewed me, except one who was probably my age.
My hair is still short, but not a pixie, like it was. I think that style was just too severe for me and actually accentuated my laugh lines, which make me look old! Realistically, it's not age, it's genetics. Both of my parents had laugh lines, but other than that looked very young.