Original 3 tab shingle roof installed in 1996. Villa Hood Gutter SYSTEM in 2004. Curently there is a leak around the extra large natural limestone fireplace. There is a missing 3-4' section of metal ice guard missing. About 6 years ago we noticed black streak on the roof, we cleaned it and installed zinc strips this helped with the black streaks I believe in the trade it's blue-green algae? We are located in NE Ohio with severe winters and wind year-round. We had the dangling zinc removed before it damaged shingles but the black returned. We are considering IKO Cambridge and GAF Timberline HD shingles withcertified installers and warranties. Question1. The GAF installer gives a 10 yr warranty for parts and labor with and without a tear off the IKO is 10 with tear off 5 without. BIGGEST CONCERN would anyone shingle over this particular situation? I realize no matter how many years these lifetime warranties cover no one has seen a shingle last that long, I am not about to speed up the wear and tear to save a few thousand $$ now to spend many $$later. Hubby has other ideas and thinks if these guys are willing to warranty both why not? I feel a warranty call would be hard enough without giving the co. an excuse any experience with either of these co's and warranty issues? Also speaking of warranty issues the roofers are not wanting to void the gutter warranty by removing them and reinstalling them and say the only way to avoid this is to do a complete tear off. Any ideas here? The house is a 1950's California style ranch home with 3-4' overhangs. With theiceand water shield having to be applied in 6-12' widths/depths I am concerned with creating uneveness if the remainder of the roof stays in place. AS WELL AS THE ALGAE how will it affect the new product and its life expectancy. Any insight would be greatly appreciated.