The coastguard I talked to said keep them as spares, but ....
The rocket ones use a spring to launch the rocket body out of the tube - this becomes week over time thus rocket starts in tube - so you might not want to be holding it
From previous practices(remember to get permision from the coastguard) pin points and smokes work for a while (remember to be up wind or you are Tango man!
), mini flares either work, make loud band and no colours or don't.
But what do you do with a flare you have fired but has failed to work - ie a mis fire ? deep 6 it? I wouldn't want it anymore.