How often was the oil changed? What type of oil are you using? Seems to me that once the oil gets up to temp it will absorb the moisture still present. The rust may dissolve in the oil if it has a high detergent package to it. I'd probably be diligent about oil and filter changes though the rust is probably from condensation and the possibility that the engine was ran cold too often. I have had engines that had steam type vapor come from the breather until the engine warmed up.
Just a thought
"As I lay rubber down the street, I pray for traction I can keep, but if I spin and begin to slide, please dear God protect my sweet ride." -Amen
56 Chevy 3100 
