Cluster feeding help!

Ma

So my LO has been cluster feeding twice in a day. During the day is fine because we’re up and about. But at night I struggle to know when he’s done. After nursing for like 3-4 hours he’ll sleep on me for like 10-20 minutes then I’ll put him in the bassinet go lay down and within minutes he’s crying for more. How do I know when he’s officially done and I can rest?