When you duplicate a well-performing Facebook campaign, Meta treats the duplicate as a brand-new campaign, which means it re-enters the learning phase. This can result in different performance outcomes, even if all the settings, creatives, and targeting are the same.
Duplicating isn’t inherently bad, but it depends on your objective. It’s a smart move if you want to test different audiences, creative angles, or campaign structures (like CBO vs. ABO), or if you’re scaling with a separate budget.
However, it can be risky if you're expecting the duplicate to perform exactly like the original or if the original campaign hasn’t fully stabilized yet. If your goal is simply to scale, it’s often better to increase the budget gradually on the original campaign rather than duplicating it.
Always make sure you're duplicating with a purpose, whether it's testing or isolating performance, not just hoping for identical results.