Generally speaking I've not had to deal with spring breaks in some time, the last couple of people I know of breaking a set within the 3 months period both have quite an aggressive style and go way above their weight range, you have to also take into consideration, how much you are actually bocking in them 3-4 months, as if you're putting in quite a lot of hours, this could account to someone elses 9 months of bocking.
I know some people just don't suit the PJ springs, due to their style, Kiola instantly springs to mind so if you are going through so many I would say try another brand and see how you do on them.