I was just reading Charla Krupp's "How Not to Look Old," and she covers the issue of going lighter as you get older (p.23):
"The older you get, the lighter you go ... almost everyone looks better with lightness around her face. Whatever your current shade, go just two shades lighter than your natural base color ... that's because 'hair that's too dark emphasizes the lines on you face by throwing darkness into them' ... You can lighten up the strands that frame your face even more than two shades with highlights, the makeup you never take off. You'll create a halo of warmth -- brightening up your face, illuminating your skin tone, and giving you an all-over glow."
Wow, that sounds appealing. I think I need to try that. I haven't changed my hair style for a long time. I used to get highlights in my late-20s/early-30s, then stopped. Lucky for me my next-door-neighbor is a great hair stylist/colorist; she keeps wanting to put highlights in my hair. I'll have to take her up on that!