In your 20s, go dark and dangerous. Rim the full eye in jet black liner and intensify lashes with coats upon coats of mascara. Or, better yet, throw on some falsies. Add deep metallic shades like gunmetal or bronze to the lid from lash-line to crease and, as always, blend. Take the same shade and sweep it below lower lashes to pop the eye.
In your 30s, lighten up! Select a softer metallic hue like copper or pewter. Deposit color from the lashline to crease and below the bottom lashline. Smudge color with your finger so the look is more smoked out. Apply a lengthening mascara and eyeliner in black or brown in a thin, precise line.
In your 40s, keep it clean. Use metallics to brighten and open the eye only. Apply a light eyeshadow on the inside of the lid and blend a darker shade on the outside. Just of flash of metallic highlighter in the inner corner is all the drama you need. Add a coat of mascara and simple liner to complete the look.