Repeated interaction, observation, and credible commitments can change the game. They do not guarantee cooperation: mistakes, power differences, and an approaching final encounter matter. Moral reasons may also favor contribution independently of personal gain, so distinguish the strategic question of stability from the ethical question of what each owes.
In the garden example, a shared maintenance agreement can change incentives by making commitments observable. But enforcement itself raises ethical questions: who sets the workload, who excuses illness, and what happens to a resident unable to pay? A successful cooperation scheme needs a practical explanation of stability and a moral explanation of its terms. A rule can keep people contributing while still distributing burdens unfairly, so those two assessments should remain visible.