Building an API interface for airconditioning automation

[Steve-Mcl]

Oh wire the inject to a function block that does a bit simple math...

var timestamp = flow.get("timestamp");
var diffMS = Date.now() - timestamp;
const maxMS = 72*60*60*1000;//72h in ms
if(diffMS >= maxMS){
  return msg;//trigger next node
}
return null;//don't trigger next node

^ untested code - but you should get the idea. ^