I have recently had my roof renewed for the SECOND TIME! The first time was almost exactly 5 years ago. When checking the eaves before the renewal, there was very little grit in them. I feel that is proof that the process works. The process softens the shingles and therefore helps the grit to stick. I consider it maintenance, almost like changing the furnace filter. Much less expensive than replacing the shingles when they start to curl!
Don Henricksen