Chancellen, it depends on what you mean by shortspear and longspear. I do know that Gil Galad’s spear was named (I don’t remember it off hand), so this would apparently indicate that this specific spear was used over and over again.
Therefore, it would not be used as a javelin (
jaculum) or the
pilum, the longer
jacula were thrown once and then forgotten.
Pila, likewise, were one-use weapons, the soft iron neck designed to warp on contact. They were designed to stick into an enemy’s shield, bend to the ground and render the shield useless.
The
pilum was often thrown as well as used for melee, and was thus a more useful and common weapon than the
jaculum.
Longer spears, such as lances and aunurgiths, were used during the medieval period as either crouched lances by horsemen, or by footmen in shield walls and the latter
schiltron. In either case, these longer spears usually didn’t last in one piece long after their initial use. They were all disposable weapons.
The only spear type I can remember that had any re-usability value would be the Roman
hasta, a spear a bit shorter than the more common
pilum with a spear head resembling an arrow head that was used for thrusting while in tight formation.
I don’t see any reason why there wouldn’t be bill-hook type polearms in Middle Earth. After all, the conception is pretty simple, and like the flail, any farmer would be familiar with the bill-hook as a tool. Such weapons require very little skill to use, and are easily made.