Yeah there's definitely no set formula. Usually in the early game you got the most tiles to improve but the fewest amount of workers. I certainly would rather in that part of the game have more archers and fewer workers to drain my GPT though. Unlike many here, I tend to feel 1 per city is overkill. I mean, by the time you're popping out cities past the 4th, aren't the first 4 fully improved by now? So what do you need more workers for? I think efficient use of 2-3 workers is ideal and won't put a drag on your economy. I do usually disband free workers I come across during conquest, *after* I've used them as labor to build a road back to my territory and repair pillaged tiles. But yeah, there is no point in having a crapton of workers milling about. After what, like turn 100 if you're slacking, literally all your tiles are improved, so what do you need workers for? You need one or two stored away to repair war damage and improve oil in another 100 turns.. so yeah, delete all but the last couple.