I am not trying to say that you are never supposed to take medications long-term. I take medications, too. Unfortunately the causes are known (or rather, there is a diagnosis), but there is no treatment or cure.

What I am trying to say is that after the Nth time you would take the kid to the doctor to find out what causes the pain, instead of just giving them painkillers. It could easily be something treatable, or rather, curable.