Originally posted by eyrei
The reason war weariness is a problem for you under republic is probably because you are the aggressor. If you are patient and a little crafty, you can get the AI to start a war just about anytime you want. When you are attacked, war weariness in republic does not set in at all for about 20 turns, and sometimes more.
That's true, I usually am the aggressor.

I've had little luck getting the AIs to declare just the war I want, when I want it. I often start wars with complicated sets of MPPs in place. Carefully timed wars with a window of opportunity of just a few turns. I'll have to try again in my next game but in the past I haven't been able to get the AIs to predictably declare war under these circumstances. I also do tend to get into phases where war lasts a lot longer than 20 turns

There may be short intervals of peace between one war and the next, but the game seems to remember recent (within 20 turns? I'm not sure) wars and count them toward war weariness if you go to war again.
I've just done some quick tests in a game I'm playing which is currently at the "milking" stage. These numbers are for an extreme case, not representative for earlier stages of the game and normal size maps. Nonetheless I think the numbers are interesting, they may help to highlight the underlying factors. They certainly seem to confirm my thinking that Communism is largely useless.
The game has about 350 cities. It has two high production core regions where the cities have most improvements. The rest of the cities are mostly around size 12 at this time, either working on their Hospital or their Mass Transit. Almost all cities have Marketplace and Aqueduct.
I played from my current save through a revolution to each government, then played one turn under the new government for things to stabilize, then noted some numbers. I kept the science and luxury sliders at zero.
Democracy: gross income 13476, corruption 8837, net income 3340, mfg.goods 2144Mt.
Republic: gross income 13438, corruption 8896, net income 3243, mfg.goods 2094Mt.
Monarchy: gross income 8367, corruption 5398, net income 1907, mfg.goods 2057Mt.
Communism: gross income 7549, corruption 6210, net income 277, mfg.goods 487Mt.
The gross income in each case includes 512 from taxmen and 50 from interest. The per turn maintenance in each case was 1062. (Lower than one might expect because of wonders.)
The "mfg.goods" number is from the F11 screen. I am not positive but believe this is an indicator of the total after-waste shield output of the Civ.
Communism: Without the taxmen contribution the whole thing is running at a net loss! Even with both sliders at zero. Perhaps Courthouses and Police Stations would solve this. I doubt it though, I suspect they'd just barely pay for themselves if added to all cities. As if that wasn't bad enough, the net shield production is really sad, about 1/4 of the other governments. Even though this size of map is a bit extreme I think this does show that Communism doesn't work well when a Civ gets large

I'm not sure if there is a cutoff point at some size. I doubt it - even at a much smaller size the penalty would be noticeable I think, and it wouldn't make sense to me to add Courthouses and Police Stations in remote cities. They'd just be useless expenses if reverting to another government. And it de-focuses production capacity, it all just adds up rather badly.
Republic: Losses in gold and shields (presumably due to corruption) are very small vs. Democracy. So the Democracy/Republic tradeoff only really matters in the other areas, i.e. worker productivity and war weariness.
Monarchy: Losses in shields vs Democracy/Republic are small, not a significant factor. Loss of income is significant. While running a war the income loss would probably be a bit less than shown by these numbers. When I was last at war in this game I had about 300 more military units, which would reduce the net income under Democracy/Republic by that much in the comparison. Still, it is clear that there's a gold (and research speed) cost to running a Monarchy. I do think that this cost would quickly disappear if one has to set the luxury slider up to sustain a war under Democracy/Republic.
I'm not sure what I learned from all this

I do think that Monarchy still suits me best for most of the game.
