Depends on the humidity in the area you are. I use a tent with screen walls and a rain fly. I chose synthetic for my sleeping bag because of moisture. When camping at lower elevations along the east coast of the US I get some dampness almost every night. If the morning dawns bright and cheerful I will lay the bag out to dry a bit and pack it last. If it is a wet day, I just pack the bag and hope for the best. If it gets really wet, I will dry it at the first chance I get, whether by sunlight or other means.

Aaron