I've only bought the pan a week ago and used it three times. Hot dogs, eggs, and steak.
When I'm done I clean it with a scrubby sponge and once with a little bit of detergent, then put it on the stove to dry quickly. Then while it's hot I smear maybe a teaspoon of vegetable oil on it with a paper towel "brush".
In between uses it's wet with oil, as you can see in the picture. How much residual oil should there be? I had the impression that it would be dryer.
Also, how much should I scrub? I am not going to leave crust of beef on there, but I also don't think it's supposed to be scrubbed back to new smoothness.
Does this take into consideration how much longer the water will be there as it evaporates at room temperature to how much shorter there will be any water present for any reaction when boiled away instead?
I guess it depends on what you mean. Either way, you should try your best to dry off your cast-iron utensils with a cloth or something like that. If you're rinsing your pan, pouring off the water, and then just setting it down, you're asking for rust either way. But, applying heat to evaporate the water is giving the oxygen atoms a better opportunity to form ionic bonds. And remember, not all evaporation is due to heat. Heck, it would be interesting to find out if boiling off your water by quickly pulling a vacuum around the cast iron would be an effective way to reduce rusting.
If you like to leave your cast iron pots and pans very wet, then you're probably creating a pretty good environment in which the water can absorb carbon dioxide and form carbonic acid (the thing that makes a glass of water that's been sitting out all day taste "stale"), which will really exacerbate the rusting.