Sun exposure matters more than age
The single biggest factor in how long a cedar roof lasts here is not the age of the shingles, it is how much sun and airflow the roof gets between storms. An open, south facing roof dries out relatively quickly after rain and can hold up for decades with routine maintenance. A shaded, north facing roof under dense canopy, common on a lot of Lynn Valley and Edgemont properties, stays damp far longer and typically needs more frequent attention, sometimes on a noticeably shorter overall timeline.
Installation detail that shows up years later
Proper spacing between cedar courses allows water to drain rather than sit at the butt of each shingle, and roofs installed with tight spacing to save material often show accelerated rot at exactly those points, sometimes well before the shingle's expected lifespan would suggest. Ventilation underneath the deck matters just as much. A cedar roof over a poorly ventilated attic traps moisture from inside the house as well as dealing with rain from outside, and that combination shortens its life from both directions at once.
These are details that are effectively invisible once the roof is installed, which is part of why we check the underlying structure carefully on any cedar roof we take on, rather than assuming a roof's visible condition tells the full story.
The role of ongoing maintenance
A cedar roof that gets regular moss and debris removal, along with prompt replacement of individual split or missing shingles, consistently outperforms an identical roof left unmaintained, regardless of sun exposure. Maintenance will not overcome a genuinely bad site condition, but on a reasonable lot it is often the difference between a cedar roof that needs full replacement after a couple of decades and one that keeps going considerably longer.
Signs a cedar roof is nearing the end
Widespread curling and splitting across multiple roof planes, rather than isolated spots, is one of the clearest signs. So is a shingle that cracks the moment it is lifted for inspection, which tells us the wood itself has lost the flexibility that lets cedar shed water properly. At that point, ongoing spot repairs stop being a reasonable long term plan, and a full rebuild, either back into cedar or into a different material suited to the lot, becomes the honest recommendation.