After about 6 weeks: Fill nail holes in with wood filler and stain or apply water repellant.
Cleaning: Clean you new steps with mild soap and a pressure washer.
Shrinkage: As wood dries, you can expect some slight shrinkage in both width and length.
Checks, splitting and grain separation: As wood is exposed to alternating cycles of weathering and drying, some checking and splitting is to be expected.
The lumber is treated against rot, fungal decay and termite attack.