And Starscream screaming what he would do with Megatron's... non-existent whatever part he did the deed with... during labor... *sporfle* Thanks, this made it all better.

The Creation Matrix is what probably makes the new bots if and when they need ones. You could also stretch that the female/frailer-looking ones have the same function for backup if the leader is in shit condition (TF movie) or in battle or emergency. Actually I think they'd rarely need new bots so making one would be a big event. But I can see Optimus all smiley and welcoming the new one in a father-kind-of-way xD I'd also guess a new bot would already have a vast amount of encyclopedia knowledge and maybe even a predetermined function, but would need time to sort out his own reaction to things. And maybe I'm giving too much thought to this xD