No we do not shot peen.  Testing has shown that shot peening is most beneficial in heavy material like big truck springs that are using full taper leaves.  The big point here is that all springs-whether they’re leaves or coils-begin their fatigue cycles on the very first day of use.  Every time the spring flexes up or down is a cycle.  Try taking a thin piece of metal and bend it back and forth until it breaks. Note the heat generated and the small crack at the bend.  All springs do the same thing-over a much longer span of time, of course–and all the shot peening in the world won’t change that.