After cooking something greasy that doesn't stick -- like fried eggs or a grilled cheese sandwich -- in a cast iron pan, the best thing you can do for the pan is let it sit for a few hours rather than washing it right away. The grease coats the pan as it gradually cools and improves the seasoning.
See, I'm not letting my lunch dishes sit because I'm lazy. I'm seasoning the pan.
To clarify, I am also lazy.