When do you replace your roof due to lack of granules?

Missing granules, when viewed from the ground, look like dark patches on light shingles or lighter patches if the shingles are black or dark.  You will also see large amounts of granules in the gutters when you clean them.

The loss of granules do not affect the waterproofing of the roof, so if they are missing you won’t necessarily get leaks.  But the granules protect the asphalt in the shingle from being damaged by the UV rays of the sun. So once they go, the shingles will wear out faster.