Peaster,
What I meant to say was that the 130 gold threshold was rather low if you were rush buying the caravans, which is how I understood your comment about 130g being the aproximate value of 50 shields. 130g is decent if you are sending out a caravan that was not rush built ... and I eventually had trouble finding cities to rush build caravans in...
No ... The history of the van [rush built or not] doesn't matter! This is clearer if you play using a value system. In your extreme case, where each van is RB'd and only gets a 130g average return, the van system is barely sustainable. So, aim for an
average return of at least 200g, so that you are making a clear profit, and trade is helping you achieve your other goals in the game. If a few vans only return 130g, I wouldn't consider them to be mistakes, but they aren't really helping with the sustainabliity issue. I'd consider a 40g van to be a pretty clear mistake [some players seem to be happy with them, but haven't explained clearly].
I understood your comment about getting blocked. To summarize my response; 1) Try to deal mainly in Hides, especially in the first half, so that blockage is a non-issue. 2) Keep making more cities, so that if some cities get blocked, you have others. 3) The alternative to making a 130g van and getting blocked is - wait and get blocked later. This may be OK if you are in the middle of a republic-growth phase [so your expections for bonuses are growing very fast] but interest theory suggests it is normally better to get the bonus ASAP and re-invest it. Also, acccording to solo's work, the sooner you get blocked, the sooner you get unblocked [on average].
It really depends on why you are sending the caravan.
I partially agree, in the sense that there are exceptions to every rule [except maybe in mathematics]. I think my guidelines apply in most situations, but I have made some assumptions, which are based on lots of games and discussion. Maybe these assumptions are debatable:
1) The initial bonus, especially the gold part, matters more than the ongoings. The only exception I can imagine would be for celebrating. But [at least in my games] celebration usually isn't that hard to achieve, by building WoWs and/or moving up the luxury bar for a short time. In a fairly large civ, the costs involved are negligible.
2) You have decided that your map can support heavy trade, and you have invested wisely in that strategy [for example, if playing on a small map, with one continent, I probably wouldn't bother to trade at all]. So, you are getting frequent bonuses, averaging over 200g, and trade is helping you achieve your other goals [growth, conquest, science, whatever].
3) You have some rational trade and/or growth strategy in place. I am thinking of the Hides strategy I mentioned already, or something like ICS growth. I suppose there are many others. You are playing for conquest or landing, without excessive delays. I am not sure if my rules apply to games for High Score [but as far as I know, those games do not require any particular trade strategy] or to OCC, multi-player, etc.
I really don't have a better guideline to suggest than yours, however. I usually decide what is reasonable based on the individual circumstances of the game. If, for some reason, 130 gold was the best I could do, I might send a few ships out from time to time, but I wouldn't bother establishing a shipchain, because the returns wouldn't justify the expense.
OK. It is wise to adjust to specific situations. On the other hand, Civ2 is fairly complex, and we can think more deeply about it with a foundation of general principles, or even a value system, rather than starting from scratch each time. I think this is proven in comparison games and pbems. [also, about the shipchains, see assumption 2 above].
What I was trying to get across regarding the gold, science, and shields is that an "exchange rate" between different products might change as you try to "exchange" them to a greater extent....
Yes, the fair exchange rate is somewhat variable, but it is not arbitrary, and not useless. The rates I posted are fairly accurate for a "generic" Civ2 situation. Along with some basic math, they are very useful for "generic" decision-making. For example, making improvements in order to sell them for gold is usually a very bad idea. Granted, there may be some rare exceptions to that, but this is usually a no-brainer. Other decisions are more complex - Shall I place my workers on fish or forest ? Should I rush buy a settler, or a van, or neither ? What is a fair price for that AI city which I want to bribe ? Should my settler stop to build a road ?
If you don't like making decsions randomly, and I don't, you can evaluate all these with math + a value system [+ a little healthy skepticism]. As I said, it doesn't work perfectly, but it seems to work better than the alternatives.
About Human Opponents: I cannot speak much about online multi-player games, since I've only played a couple. But I have played in several PBEMS. In those, it was quite rare for a human player to destroy another player's vans. In many cases, the humans formed alliances, actively welcomed foreign vans, helped with transportation issues, etc. In other cases, the humans were at war, but enemy vans still sneaked into coastal cities from boats. Maybe others have different experiences ?