This came up in another post but is important enough to merit clarification. My fire extinquisher has been on my boat for a LONG time. The little dial always reads in the green so every Spring when checking out flares and all the other safety equipment I simply assume it is OK and move on. There are no signs of corrosion or other wear.<br /><br />Is (a) this a fair indication that the thing will work? or (b) should they be replaced every x years regardless.