How often should knives be sharpened?
For a home cook: Honing should be done before or after heavy use or once every couple of weeks, depending on how finicky you are about the blade itself. Proper honing can stave off the need for an actual grind/sharpen for years.

-Honing realigns the existing edge. Just a few strops on each side of the honing steel. It doesn't take much.
-Sharpening grinds it down, takes away steel, and makes an entirely new edge. It's not something to be done often, or even routinely. I get mine professionally done at a kitchen shop.

If you're a pro, you want to hone any and all serious knives before each shift.