I see you've already been discussing this with an AE via SR 42727384 - we had an internal discussion about this yesterday.
It only takes 100 (50 normally, I think it depends on other settings) iterations if it hasn't converged before then. Setting it lower won't help it converge, but would potentially just let it give up sooner. Anyway, right now it is not possible to set maxperiods lower than the default - it's normally used to allow more iterations for it to converge, which is only rarely going to help.
The fundamental issue that needs resolving is why it is not converging - or if that convergence is slow. You should work that through with the AE dealing with your service request. We're also planning on documenting the behaviour of maxperiods so that it is clearer.