Couple questions about castles

[Severus]

Its becoming apparent that its completely unnecessary to have but a couple castles for troop production, as I don’t seem to need castles for their defensive capabilities (Its a shame the AI is so ineffectual when performing sieges) In the game the main function of castles is to produce non militia type troops. While its true historically that barons would have knights on the payroll residing in the castle, a castles function wasn't to build armies. The only advantage I see to having a bunch of castles in the game is to produce troops closer to the action. I know it can depend on circumstances, but I’m curious, how many settlements do you guys leave as castles in the long campaign? Also when converting from one type to another do you have to manually destroy the buildings? I was thinking it would make sense if the destruction and recoup of funds was automated.
I'm disappointed as i was hoping castles would be an exciting innovation in game play. During the late middle ages the construction of castles were often an absolute necessity to establish strong centralized rule against local fragmentation, and especially in newly conquered lands. In the couple games i have played so far the only thing castles are a necessity for is producing troops.

[PBI]

Castles have much better public order than cities, so they are quite useful to have in very far-flung, relatively poor provinces such as Jedda or Tripoli to avoid having to maintain a huge garrison to keep order (a castle will almost never rebel even if it has a garrison of only 10 peasant archers say). So they are useful for securing control of newly conquered lands, as you suggest they should be.

I think most people find they end up with many more cities than castles as their empire expands. I usually aim to have roughly one castle per "region", i.e. one in Spain, one in France, one in Britain etc, with the rest cities. It's quite useful to have castles on your borders however as although it is easy enough to defend a city, defending a citadel is even easier; also, I think the AI may be more averse to besieging castles than cities, so it should help to deter them from invading.

[Ratwar]

Personally, I've found castles to be quite useful for border defense. I mean, once you can upgrade an area to a Minor City, sure they aren't that useful, but a castle with Stone Walls is much easier to defend than a Town which can barely kill anything. You can really see this in the Russian campaign. If you turn all of the easter castles into towns, the Mongols will roll right through them.

Also, I like to have some near my border for troop retraining needs. It is a lot easier to fall back a one-turn march than spend ten returning to your troop base.

[Severus]

I certainly agree that a castle is much better for defense relative to pallisades but once my cities have a good set of walls up feel pretty darn confident. I didnt realize public order was given a bonus for castles, i just assumed that it was due to the moderate tax rate. It would make sense for the computer having some apprehension attacking castles, just because its a castle, even if they arent well garrisoned.
Im actually playing a long campaign (first time, havent had the game long) with Spain where i have conquered a couple cities next to Jerusalem (I gifted the holy city to the pope, There was a heretics and Imam festival going on so he can have it until i get some cardinals and assasins overthere!) Since they are so far away from Spain do you think its best to convert these to castles? They should be excellent cities to develop trade, but I have just gotten the "mongels are coming" message so maybe that wouldn't be prudent. btw if anyone off the top of their head knows about possibly recouping florins when conversion takes place id be interested to hear!

[Rhedd]

I never convert cities or castles. Ever.

Just take them as they are, no matter what.

Not only does this put you on much more even footing with the AI, but it makes the game more interesting, as decisions on what province to take next can be greatly influenced by its settlement type.

[Monsieur Alphonse]

I always try to group some castles. For instance Caen / Angers or Bern / Staufen or Hamburg / Magdeburg. This way I can train a stack within a couple of turns. Castles at the front line will be useful not only for defense but also for retraining depleted units.