In Canada, most types of boats are required to carry Canadian-approved flares less than 4 years old from date of manufacture as mandatory equipment (The Canada Shipping Act) - dates are stamped or printed on all flares. Flares under 5 years old should be safe to keep for back-up if stored properly. Recent changes permit the number of distress signals to be reduced by half if the craft has a two-way radio or cellphone.
Be sure to keep all your signal products dry and protected from heat in a labelled waterproof container or ziploc bag. The chemicals in the flares break down over time and they can misfire and injure anyone nearby. It is illegal to fire a flare if there is no emergency. Keep away from children - they can kill!
Flares are considered to be hazardous material and must be disposed of the same as explosives and fireworks. It is no longer permisable to set off expired flares, and they are not accepted at landfill sites, or by police or fire departments. To help boaters dispose of expired flares in a safe and environmentally responsible manner CPS-ECP (Canadian Power & Sail Squadrons) and selected CIL Dealers are hosting Disposal Days where you can bring your outdated flares to be properly disposed of, free of charge.