At a population of over 70, I've just pierced the aquifer. I'll finally be expanding underground as soon as I've got the drain set up and the hole patched up. Despite not having mines yet, and my military being outfitted almost entirely in copper, my metalworking industry is utterly voracious, I can barely import metal fast enough to keep pace, and I've been buying every single metal item the caravans have to offer. The elves have declared war on my, despite me not having ever hurt them or offered them wood (I think they dislike the fact that at this point I've turned thousands of trees into charcoal). My baroness is incredibly susceptible to stress and just got out of prison - she was in for punching a pig just before becoming baroness.
On the plus side, I have plenty of platinum statues, every dwarf has a crossbow and ammunition, all the dwarves are wearing at least leather and bone armour with a copper mail shirt, I have defeated an undead siege through direct combat without traps (crossbow zerg ftw), the hospital is effective and stocked with soap and clean water, and tantrums are rare.
Also, my head doctor, who was appointed with no skills from the starting 7, is now a Legendary diagnostician. A lot of stuff has gone down these past four years.