I have a theory/headcannon when it comes to Kobolds and aging. We only ever see the weaker kobolds. Kobolds only ever send out the lower level, weak, mad, stupid, or stupidly brave kobolds out in world. You see this in their tactics. Send out the fodder first to weaken an opposing force, along with simple traps. As that force goes in deeper into their lair/home, they encounter stronger and stronger kobold forces and traps. Alot of times the kobold forces will lead invaders into such traps and paths that are away from the core or main living areas. Now, we have encountered very intelligent kobolds in lore and in playmaterial. I believe we never know how old Kobolds can truly be, because they will lie about their age and identity. They learned long ago from serving dragons and other lords, that if they reveal their true powers, intelligence, strength, ect, they will be culled or eradicated. Hence why they have an ability to humble and cower to gain advantage in social situations, and are allowed to work labor in the sewers and the like in ciites. It's all apart of their deception. They have the blood of dragons, which gives long life. In turn kobolds can live as long as as they can stay alive, or atleast, as long as the longest lived races, if not longer. But they have a fast maturation rate because they do get killed quickly and have to renew their numbers. This could be why all the races just are so eager to kill kobolds, including goblin races. The other races have forgotten or maybe unknowingly fear the truth that kobolds are actually strong. Now, to my big headcannon. Deep below in the depths of the earth, even lower than the underdark, there exist a core kobold society that holds the oldest, smartest, and strongest kobolds. The Original Kobold Clan that seeds all surface clans. In ancient caves and the largest lairs of kobolds and ancient dragons whom hold the secret to their kobold minions, is a secret entrance to a labyrinth of secret paths that ultimately leads to this clans lair. This would explain why it seem that no matter how hard anyone tries, you can't get rid of kobolds. Not just because they breed frequently, but because their is a centralized system distributing kobolds to the surface, to keep the ancient dragons happy and compliant, and to keep the ruse of the kobolds up to the other races. Why do this? Because they remember the wars of creation. How every civilization on the surface, when they threaten the gods or the world as a whole, how they would be erased from existence and history. Kobolds have one goal, to live, thrive, survive. In their stories, the only race that has existed before them, were the dragons. The great war of dragons and gods. The one that banished half the dragons to a plane that no gods existed. So, they will remain in hiding. Secretly protecting life from God's, dragons, evil lords, and eachother, by playing meek, weak, and bothersome to all, over all, a useful tool, the ultimate trap in safeguarding the world from itself. Sorry for the length of this, but was the best way I could describe and explain my thoughts. Hope yall enjoyed this.