So currently i'm in school for Mechanical Engineering, though I got a general question. I could have sworn that I read in my physics book working up to the point I am now reading that as long as a spring isn't pushed past it's stress point that it should last forever. Though now I have had someone trying to tell me that it would last only so many cycles and wear out over time ??? I'd suppose this would be somewhat important to know for sure when designing machines. If anyone could answer that would be great. Thanks.