The reality is that many factors go into a female ball pythons decision as to wether or not her body will produce follicles and allow them to be fertilized. Age, weight, weight to length ratio are just a few.
What are some of the other factors? Probably genetics, recently laying or not, being bred multiple seasons in a row, what else

And speaking of bred multiple seasons in a row, how many years would you breed a girl in a row, provided that each time she has good size? Wouldn't she eventually just poop out, or would you keep going if there is no apparent reason to stop?