These devices use a variety of chemicals, all of which can deteriorate over time, either limiting burn time or altitude, or causing the device to fail altogether. We found expired hand-held flares that were very hard to ignite or didn't seem to burn as brightly as they should, and meteor flares that didn't fly as high or burn as long as advertised claims. A few failed to fire at all. From our experience, small boats in daylight near shore and with heavy boat traffic should consider carrying three hand-held smoke flares to guide assistance to them. Big boats on large bodies of water and night boaters may be best advised to carry aerial meteors or parachute flares to attract attention and handheld flares for help to home-in on.
Smoke is the best option for day only signaling.
Also consider that exposure justifies expenditure. Attending demonstrations of proper handling and use of these devices that are offered by many U.S. Power Squadrons and U.S. Coast Guard Auxiliary flotillas is a great way to gain firsthand knowledge. Devices must be in serviceable condition, dates not expired and stowed accessibly. Exceptions are recreational boats less than 16'L, open sailboats less than 26'L and not equipped with propulsion machinery, and manually propelled boats. These vessels are only required to carry nighttime signals when operating from sunset to sunrise.