Tech brokering

Can someone who has actually played with tech brokering turned off on huge marathon maps share their experience.

Especially at Emp and then Immortal.

Also, a pointer at good discussion of tech lines and AI tech strategies would be helpful.

The biggest change on higher levels is that the AI's can no longer trade everything around to cover the holes in their research, leaving more opportunities for the player to sell fewer monopoly techs for lots of backfill. If you can determine which techs will still be monopolies by the time you get them, you're laughing. For instance, there will be much more available from the usual techs like Aesthetics, Music, Philosophy, which the AI's won't prioritise if the player gets there first.

This means you're able to avoid having to trade AIs useful techs like Currency, Civil Service to keep up yourself, leaving weaker AI's much further behind in the tech race.

Also, there should be a bit more gold available to trade for, more of the time due to less available AI-AI trades. Selling stuff you've teched is therefore easier, which allows you to power 100% research more of the time.

I've played a few games recently with these settings (except usually large rather than huge maps).

The main difference with no tech brokering is that monopoly techs are more valuable, since you can take your time trading them to each civ and wait for them to have something worth having. Not quite indefinitely, as eventually another civ will research it, but you don't have to just acept whatever gold is on hand when you trade it away.

The AI actually has one relatively smart trick which only shows up with no tech brokering. If an AI has a tech which you are currently researching they'll often call you up a couple of turns before you complete it offering to sell it to you cheap. This might get you the tech a bit earlier, but will also prevent you trading it to anyone else. Unless everyone else already has the tech, think carefully before you accept in this situation.

There are tech lines that the AI tends to avoid, and so are good sources of monopoly tech even at Emp/Imm. Alphabet shows up surprisingly late for most AI, and can often be used to backfill most available techs once you get it. As already mentioned the Aesthetics/Literature branch stays unresearched quite late, but the beaker values are low compared to other techs showing up at the time. In the midgame Replaceable Parts -> Rifling is often left late (but you may want to think twice about trading Rifling away). Ditto Astronomy. Biology -> Medicine is also good if you're planning to get a lot of use out of Sushi, since medicine has a high beaker value and is almost completely ignored by the AI. It's also not actually very useful to the AI once Sushi has been incorporated.

Conversely there are paths the AI tends to beeline, and so are best avoided and backfilled. Unless you're going for a religion or wonder heavy strategy you can avoid techs such as Meditation, Polytheism, Theology and Divine Right as the AI tends to grab them fast making them easy to trade for and harder to monopolise. Feudalism and Nationalism seem to be favourites of the AI - these invariably show up long before I get them.

This definitely hurts the AI a LOT

I always disable tech brokering, simply because it slows down the tech pace a bit (I simply don't like 16th century tanks) and relaxes the competitive tech trading business a bit. You can safely trade a tech to one civ, without having to trade away the tech to every other civ right away (otherwise they would do it for you). More realistic imho.

Tech monopolies become even more valuable. Benificial tech paths are beeling alpabet, then currency, and then the aesthetics branch.