Ok, we've seen their planet of origin with the lake full of symbiotes, we've seen their leaders, the system lords, the local governors under the system lords and the barest handful of scientists and assasins, but where are the rest of them?

Every Jaffa carries a Goa'uld larvae. Each system lord has thousands if not millions of Jaffa, making thousands if not millions of larvae. Each larvae can only remain in a Jaffa until maturity, at which point it must take a host, meaning at least a couple goa'ulds go through each Jaffa, thus multiplying the previous thousands/millions some more. Yet after all this, every single Goa'uld stronghold seems to be populated almost entirely by servants, slaves and jaffa. Surely they've got to have some cities of actually Goa'ulds lying around somewhere? Are they killing massive amounts of the larvae when they outgrow the Jaffa? If so, why? Are there some Goa'uld worlds out there where the snakes have a true civilization of their own? If so, what's there? And why has it never been mentioned?