My first daughter had many symptoms as an infant, I would say within a few weeks, although she wasn't dx until she was 14 months old. The symptoms were all due to being pancreatic insuff. Eventually a rectal prolapse led us to the CF dx. My younger daughter started enzymes at one month due to pance insuff. symptoms.
As for lung issues, my oldest was about 7-8 years old, and my younger one is following the same path...just now starting to have more problems at the age of 7.