OK, so I do not roof everyday but on occasion do here and there! As I was doing a cut valley the otherday a thought came to mind. When the non-cut side wraps through the valley using dimensional shingles there is an opportunity for water to collect in the small areas that the laminated pieces are bonded to the base shingle. I assume the theory is that the vast majority of water flows out and over these small pockets what little is left will evaporate with air and sun? Obviously this is accepted practice, but just a thought that came to mind! Obviously one can adjust the pattern at times to minimize these from falling in the throat of the valley, but you cannot always....