You should inspect your roof at least once a year. Nothing beats getting up close, but a good pair of binoculars can give you the next best thing. Look for curling or buckling shingles, shingle granules in your gutters, and other signs of wear.
Whenever you are glueing glass you must consider the visibility of the adhesive. If the glass is translucent, you will want a glue that dries as clear as possible. Before glueing any glass bond be sure that the glass is clean, free of any oil (even from your fingers) and dry.