Manufacturers rate architectural shingles for 30 to 50 years. That is the lab number. In the real world, in the Quad Cities, we typically see 20 to 25 years on a well ventilated roof and 12 to 18 years on a poorly ventilated one.
Freeze thaw cycles are the killer. Water gets under a lifted tab, freezes overnight, expands, and lifts the tab a little more. Repeat that a hundred times a winter and you have loose shingles.
Ventilation is what you are actually buying when you buy a new roof system. Balanced intake at the soffit and exhaust at the ridge keeps the deck dry and the shingles cooler in summer.