Gone are the days of 10, 20, 30, 40 and 50 year warranties and the accompanying jump in price from benchmark to benchmark. Lifetime equates usually to 50 years if you read the fine print, however, if you aim for 30 years and reasonably maintain it you shouldn't have too much worry about your roof. The best way to clean your roof is to use a zinc oxide-based powder or cleaning solution. This kills the moss and algae on the roof, it may take some time for the moss to slough off but it will work. Y...