I'm with you both... I have struggled with the fact that most of the syndromes associated with PWS can present up to a few years of age. You can be so happy and carefree one day and then the fear can come on like a wave and you worry constantly of what might happen in the future.
I try not to let the "what if's" get in the way of enjoying being a mother to my sweet little girl, but on my bad days it's pretty hard not to think about it. Hang in there.