Flares get bought once, stowed in a locker and forgotten. Years later the boat goes to survey with a box of them, half out of date and the rest close. The night one's needed, nobody wants to find out if an old flare still lights.
What the rule asks
In the US, 33 CFR 175.110 requires boats 16 feet and over to carry visual distress signals for day and night use. The accepted list in 175.130 includes hand-held and parachute red flares, three of which cover day and night, orange smoke for day, an electric distress light for night and an orange flag for day.
Pyrotechnics expire. Rutgers Cooperative Extension notes that flares must be within their 42 month expiration date and readily accessible, and that expired flares don't count towards the required signals.
How a surveyor checks it
Open the flare container and read every date. Count what's in date by type: day, night, or both. Note any electric light or flag. Check where the container lives: reachable from the cockpit, dry, and not buried under gear.
Then match it to the boat's use. A boat going offshore needs more than a lake boat, and a charter licence or race rules may ask for more than the federal minimum.
What decides the grade
Use and dates. No in-date signals on a boat going to sea is an A. Expired flares, or too few for the boat's use, is a B. A set close to expiry or badly stowed is a C.