Sieges are a difficult form of warfare because so little happens. They are often won or lost based on food and water. In this case, the advantage continued to lie with the Nephites, who had provisions to last for seven years when the first battle occurred, and had certainly worked to add to those stores since thing.
The Gadiantons still had a supply chain problem. There was nothing that they could scavenge, especially with a wilderness that had been apparently over-hunted. In Mesoamerica, if they were hunting for wild animals, there were very few that were large. Thus, they would need very large quantities of the smaller animals, and that would deplete them quickly.
The problem of food is just as difficult for those laying siege as for those who are being besieged.