For most users a maintenance dose will probably be required to hold the weight off. A few people whose weight gain was tied to a short event such as pregnancy or a medication might stop and stay stable afterward. Those who have dealt with obesity for many years usually have an appetite system that is set too high, so stopping the medication lets the old pattern return.
I found this review on weight trajectories after stopping GLP-1 drugs worth reading. It indicates that people regain about three-quarters of what they lost, which still leaves a small net improvement of roughly five percent. That is better than nothing, yet staying on tirzepatide or retatrutide appears capable of delivering twenty to thirty percent loss that holds. The regain curve seems to flatten eventually, and it would be useful to know what physiological shift causes that plateau. The paper's suggestion that people simply make better food choices does not seem convincing to me.