HI, I am a mum with a 15 yr old cf daughter. I looked at lots of the replies to your question and you are often given the 'average'. Remember that the average is worked out by counting the very very sick people who are in hopsital every few weeks and the very well people. My daughter for example has only been in hospital 2x since 2001.
I dont think anyone can really say how long YOU will live (only God knows that anyway). But I know that, good diet, lots of excercise and getting medication and physio when you need it makes a HUGE difference.
You need to ask your doctors lots of questions about YOU. Because every CFer has different levels of the sypmptoms. My daughters doctor also said, some people can be really well when they are younger and get worse and others are bad when they are young and their sympotoms improve as they get older. He also said that he knows 70 year olds with CF.
You need to take good care of yourself, special care maybe, but good care. And be grateful that you are able to sit and chat, but more than that - get out there and DO LIFE!!!!!!
All the best