Once you create a lookalike audience, Meta says it may take 6-24 hours for your Lookalike Audience to be created. Their documentation also says you don’t need to wait for that creation to complete, and that you can use it for targeting right away.
Beyond that, a frequent question I get is regarding the updating of your lookalike audience. No, you don’t need to manually update your lookalike audience or recreate it months down the road.
Your lookalike audience will refresh every 3-7 days, as long as you’re still actively targeting ads to it. If you stop using a lookalike audience for a few weeks, it will then refresh when you use it again for targeting.
This is all helpful because lookalike audiences SHOULD refresh, especially if the source audience it’s based on is also changing.
