i dont really know anything about flashes but i have a chance to get a used canon 550ex for $160. i just wondered how long these things last? i dont know much about how much this flash was used but i will find out later today. i assume you can just replace the bulb or something if it goes bad. how much does that cost? so just so i can have something to go on....how long does a casually used flash usually last? and what cost am i looking at to getting it going again when it goes bad?