As for a piece of guard rail falling -- I've never seen 26' pieces put up with only 1 attachment point.  Welds can break, bolts or redi rod can too.  Fix them when they do.   

I'm not sure on your 'crystalizing over time' theory.  I always thought that it happened at the time of welding/cooling -- or not, not something that happens 'over time'.  

something the does happen over time = rust.     :-)