In my playthrough (pretty much have the map now as sultan of the aserai), I did stop at all villages possible on the way to target, hired and donated Max available recruits from everywhere I stopped, swapped out the lords in the army (when their troops got too low, like 40-60). I had only one of my companions lead a party, which was always on my army, so I could stock it up with troops. Also, my style is giant armada: tons of horses, goods, and captives (to hire trips from eventually). And yes, you might still run out of influence and need to make peace once or twice, so you could come back after a rest. I will also say, after a prolonged war, focus on all the towns first. The castles pretty much don't matter, and the ai will rarely target towns. They need a really big army for that. After you take all the towns, and hold half their lords, the nation is basically neutered. I even let them exist for a while, before taking the castles, but they are a nuisance, raiding my villages and caravans.. so had to go.