There's a definite maximum transfer limit per week, I think it's at a max 100 food/week. However, the longer the roads are the lower the limit (I think the lowest I've seen is 15/week).
I thought that might be the case, but I can't check right now. Whatever the limit, I imagine that the larger the distance, the more intermediate destinations will "have first dibs". I'm assuming that the system is not "packet" based (in which specific packets are addressed to specific destinations) but simply "flow" based (all external demands are added up and that's what's pushed out -- and whoever taps it first wins). With almost any reasonable limit, there will be far more demand on the relatively few links to the "breadbaskets" than they are likely able to supply.
You're referring to the Chalcidean/Athenian cities on the coast, right? As long as you connect them to each other and connect one of them to a city with a good supply (usually one that has at least two more farms connected to it than it has units garrisoned, I'd say) it will eventually fill up. In the meantime, I usually use workers to bolster the stockpiles (make 5 at a time, fill them up, then disband them when they reach the target city). If possible use maxed out slaves, because they can hold double the amount workers can (cuz they have twice the people). Just be careful not to walk them through too much fog of war.
Yes, those are the ones. I've been doing exactly the same thing as you: waiting on supplies and supplementing with workers and slaves. The principal reason I was asking is to get a feeling for the break-even points: supply lines provide steady but relatively low supply per week; workers carry quite a bit, but are not terribly fast; and slaves can carry a lot, but are very slow. Given that road supply is limited, there must be radii below which workers and slaves are not efficient.
My biggest difficulty with "wait it out" right now is that I have a couple of food riots going on, most nearby locations are tapped out, and hiking in food from Heraclea Lyncestis is going to take a while.... =) I think that my main problem is that I have a habit of moving battle line units into newly conquered walled towns to quell rebellion while a garrison is raised: when they leave, they have a nasty habit of taking every scrap of food with them. In this case, I left the walls up on the cities along the coast since I don't have control of the seas and I'm worried about Athenian landings. I should probably just tear them down, disband the garrisons, and switch to a mobile defence, which is what I'll probably do tonight. That's probably what I should have done in the first place.... Live and learn.
I'm really just getting underway (pushed to the Nessus in the east, bypassing the peninsulae,; in the southwest, just took Thermopolae -- haven't even reached Corinth yet) so I'm a bit concerned that this is going to get to be a bigger and bigger problem as distances grow larger.... So much subtlety, so much to learn. Wonderful game!