From my perspective, this is a treatment you stay on for the very long haul — probably permanently — unless you weren't obese to begin with. Long-term reta research is still much thinner, but sema and tirz have both shown remarkably positive long-term outcomes, and those benefits will almost certainly carry over to reta. So remaining on it isn't harmful; it lowers your chances of diabetes, high blood pressure, high cholesterol, cardiovascular disease, strokes, cancers, possibly even dementia. Broadly speaking, the more obese, the older, and the less healthy you are overall, the bigger those effects get. There's even some data from epigenetic aging marker studies suggesting these drugs slow the aging process itself.
So if you're overweight with any health problems, or obese, staying on it helps you — and if you're at high risk, higher doses beat lower ones. Beyond those reasons, with reta or any GLP, the ideal is really to lose the weight one final time and then simply remain on it so the weight stays off; it's nearly that straightforward. The majority of people who quit GLP's after shedding weight put it back on. Some folks prefer lower maintenance doses, which makes sense when side effects are present or your diabetes or heart disease risk isn't high, and a portion of them do hold the weight off at lower doses. But at the severe end of obesity, there are strong arguments for staying on full doses long term or forever, provided side effects aren't an issue.
If the extra weight is short term or situational — say, kilos gained after an injury that kept you from exercising for a long stretch — and you drop the weight and rebuild very healthy eating and exercise patterns that you successfully lock in as firmly established habits, without having to consciously manage how much you eat to avoid regaining, then you might not need to remain on them. Yet as best I can tell, that scenario is truly uncommon. For most people, obesity is a very long term problem.