Thermal cycling
A roof in the Twin Cities lives through a wider temperature range than one almost anywhere else in the country: deep below freezing in January, well into the thirties Celsius in July. Everything on it — every nail, every sealant strip, every piece of metal — expands and contracts across that range, and again on a smaller scale every single winter day the sun comes out.
Fatigue, not wear
This is mechanical damage rather than material wear, and it shows up differently. Nails work loose a fraction at a time until a shingle no longer lies flat; a raised nail head telegraphs through the covering as a bump before it becomes an opening. The factory sealant strips that bond one course to the next lose their grip the same way. And ridge caps — the thinnest pieces on the roof, bent over the peak and exposed on both sides — are reliably first to go.
Because fatigue accumulates rather than concentrating, the signature is small failures scattered across an otherwise reasonable-looking roof: a lifted course here, a loose cap there, no single dramatic point of failure. On an older covering that pattern means the material has stopped being able to hold itself together, and patching individual spots buys months, not years.
What it means for a replacement
Two things matter more here than shingle brand. First, fastening: nail placement, quantity and depth are what stand between a covering and thirty years of cycling, and they are invisible the day the job is finished. Second, the sealing window — asphalt shingles bond by warmth, so a roof installed in the cold shoulder season may go through its first winter without ever having sealed properly. That is the honest reason the working season here runs May through October, and the reason a crew willing to install in November is making a promise the material cannot keep.