Originally Posted by gugie

Same experience. I broke one of those springs last year, but was able to carefully ride home about 10 miles after getting the chain in the big plate to take up as much slack as possible. @Andy_K had the same thing happen to one of those 3 pulley LePrees, which uses the same design I believe.
Based on my rememberance, I think the lifetime of the original Cyclone derailleurs is adequate, however unless you know it's got low mileage on one, I'd consider that there is some risk of this happening to you.