Hi David,
Slightly high glucose (mid 200's) is pretty high. Normal range should be about 90-120. That being said, the long term of effects of poor glucose level control can be devastating: blindness, poor circulation, and in the worst cases, gangrene in your feet. You're young so you'll not feel the effects now, but as with everything else, it will catch up with you. Please take care of your CFRD; your body needs insulin if your pancrease is not making enough of it.