The average life span of someone with cf is 33. But this is just a general guideline. With all of the advances in medicine, many people are living way beyond the expectancy. Both of my stepsons have cf. My youngest stepson was expected to not make it past his 10th birthday. He was on life support twice, had three heart attacks and was on full time oxygen for three years. He was put on the transplant list and recieved a double lung transplant at the age of 12. He is now 21 and has been able to live a fairly normal life for the past 9 years.
My older stepson was also very ill with his cf. He was also placed on the transplant list but sadly he passed away when he was 15. So as you can see cf affects everyone differently. It sounds like your friend is quite open with you about his cf so if you have questions for him im sure he would be glad to answer them. I found it helpfull with my stepsons that if there was something i was unsure about, I would ask their doctor, or if that was not an option, I would research it online. The cystic fibrosis foundation have many chapters all over canada and the u.s. You could phone your local chapter and get answers to many questions as well. What he needs the most is people that care about him and support him no matter what. It sounds to me like you are a very good friend to him and im sure he appriceates your support. I hope I helped and I will keep your friend in my prayers.