If an NPC still has patience after making an offer and their interest is between 1 and 4, the heroes can make another argument to attempt to improve the deal. Alternatively, they can accept the offer and end the negotiation. Let the players drive this decision. You can always have an NPC show they have patience remaining by asking, “Is there anything else?”
If the NPC’s patience is 0 or their interest is 5, then the offer the NPC makes is their final offer to the characters. The heroes can accept the offer or not, but either way, the negotiation ends.
If the NPC’s interest is 0, the NPC ends the negotiation without accepting a deal. The heroes can walk away from a negotiation without accepting a deal at any time.