My switch to Fundy ususally occurs just around the time of Tactics. I'll have one or a few of the ancient wonders & all of the second set. I'll typically have too few cities & too little infrastructure (racing for science) & avoided serious conflicts.
Once I hit Tactics, however, I'll have some opponents with muskets defending so the battles generally go my way -- time to go & conquer some. At the same time, alpines & settlers will go found new distant cities, At the same time, the lacking infrastructure will be completed. And often at the same time, the ai research will also slow down & they sometimes fight each other. I'll stay in this mode for maybe 20-30 turns, sweep up a civ or three, & research a tech or two.
Then, I'll toggle back to democracy, & watch all my primed cities explode with growth, watch the science come in at a tech per turn or two & grow to modern weapons. Once the howies come on line I'll go back & clean house.
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However, that being said, I'm learning new skills -- trade. In the current game of the month, I'm still in democracy & have just picked up robotics -- I might not get around to switching to fundy this game. I'm eager to try Andu's emissary ploy & see I can wage war in democracy, maintain the science of a tech per turn (my last two turns yielded a tech each with a zero science rate), & a spotless reputation en route to the stars.