Originally posted by Karl08
I'm not sure how it actually works, but the prognosis given me on the campaign map certainly does not count anything but units, and doesn't care how many men are within that unit, nor what kind of unit it is. I've tried a number of combinations.
Well it doesnt count the type of unit but it does count how many men are in.

The system is like so: the closer you are to the full capacity of the fort/castle the shorter the garrison will last. In this sense you can think of it as a "density" ratio of (actual garrison)/(maximum garrison). The closer the ratio to 1, the shorter their resources will last - the closer to 0 the longer.

Yes, but I like the flavour.
Indeed flavour was the aim, and it succeded - most fans prefer flavour and it played a great part in helping MTW sell more. I however prefer solid gameplay, and am far less interested in variety. STW's 12ish units were more than enough for me.