A measurement, not a rating
The score is taken at the assessment from what the surface is doing that day. It is not a rating of the house, the neighbourhood or the shingle brand, and it does not carry forward as a permanent grade.
What it does carry is consequence: the band sets the treatment and the warranty term that can be issued at that moment, which is why the number is written into the estimate rather than kept in a notebook.
What moves a roof down
The same forces the treatment is built against keep working on an untreated roof: UV breaking down the surface oils in the asphalt, daily heat cycling, water sitting where it should run off, and repeated freezing in the shingle.
Growth on shaded slopes and unrepaired leaks accelerate it. A roof that stays wet is a roof that is failing faster than one that dries out between storms.
- Granules continuing to loosen from the surface
- Edges lifting and curling as the material dries
- Water beginning to sit rather than sheet off
- Freeze-thaw pushing the shingle apart from the inside
- A leak left unrepaired, which is a repair question, not a treatment one
What a treatment changes, and what it does not
A treatment slows the wear on the surface it was applied to, which is the whole point of applying it. It does not reset the roof to new, and it does not make the score permanent.
When the roof is treated again later, it is measured again. The band on that day sets the coverage available then, which is exactly why the site never quotes a term without a visit.
Why the price lock matters here
The warranty includes a 20 percent price lock on a future re-treatment, so a roof treated now is not starting from scratch on price when it is treated again years later.
That is the practical answer to a changing score: the roof is measured, treated for the band it is in, and measured again when it is time to treat it again.