"By having Colossus in that mix, in a city that you grow to size 20"
The thing with that is, in most cases wouldn't colossus be obselete by the time your city was so big? Otherwise I agree with what you say.
The thing with me is, I'm pathetic at getting a decent science rate. In my current game it's about 900AD, but I only gat advances every 20 turns. A bit slow.
Also the immeadiate returns on caravans seem small (at most 20 coins, but mostly 4 coins), by that I mean the one off payment. I can't say I'm the best player ever, can I?! I've been using most caravans to help build wonders and only a few for trade. I'll try to do more trade. I can't trae with neighbours as I'm at war with them.