Twine and rope are rare also. Why not leather strips or something that is renewable?
I agree that they are easy to craft and renew, but IMO the very low durability is too much of a counter. Sure I can spend the day foraging and make 20 of the things, but I now have to fill my inventory with spears in order for them to be a reliable primary weapon. Would you at least consider increasing the rate at which we gain experience in maintenance and/or spear skill when using them to help offset the nerf somewhat, such that a spear focused character can achieve parity with, say, an axe focused character in the late game. I have 1850 zombie kills, 99% of which have been with a spear, and yet I only have 4 levels in spear skill and 2.5 in maintenance.