Hahahahaha....... 
This sounds like a cork and bull story eh... 
This tells something... U din study Bio....
What u mention only happens to a mother whom is about to give
birth. Her milk glands will continously produce milk, assuming that
she will feed her baby ON TIME with the amount of milk in her
breast.
However, in our very busy lives, Mothers no longer have the chance
to wait on their newborn like that. Thus, the invention of pumping
/ suction "machines", (which operate manually) serves the purpose
of releasing the "trapped" milk in the breast for their newborns.
As the mother herself will feel uncomfortable if the milk in ther
breast is store for too long. (such as headache, fever, or stuffy
at the chest area). Even if store for too long, e milk will also
not turn hard lor... Dun have to sit in the sun to melt it
lor...
