I also have a tendency to build up a lot of provinces - I like to have a province dedicated to making one of each type of unit: spears, swords, cav archers, heavy cav, light/medium cav, spies, assassins, religious types, emissaries, artillery, and a couple to build ships.

Early in the game I try to tech up at least five provinces - ships, agents, infantry, cav, and missiles. I choose which province builds what based on province bonuses and upgrade abilities. I like to get my missile troops built in provinces with iron so I can armor them (this is different from most peeps I think who armor their melee troops).

I also build all of the economic and happiness buildings in each province.

Towards the end of the game I can produce a full stack of various units in one turn.

ichi