If you avoid rushing in, many of the Campaigns can be extended to allow you to develop a large economy.

Some scenarios do insist on you playing within a timeframe for at least part of the scenario but once you learn what action on your part triggers the AI responses it is often easy to 'break' the faster game and play a slow one.

I often swap troops for villagers to beef up my economy on a temporary basis. Then as my villagers get killed or eaten I make the latest military units to fill up the population slots.

When I get REALLY bored I will play a scenario where I add as many Gold producing economic buildings across the map. This usually mean I need ot suppress the enemies but not wipe them out.... yet ;P