Automatically archive email threads with a given label after a certain number of days - https://script.google.com/home

gmail-auto-archive

function auto_archive_mails() {    
  var filter = "label:inbox and {label:blah label:foo} older_than:3d"
  var threads = GmailApp.search(filter);
  
  console.log("found:", threads.length, " threads");
  threads.forEach(function(t) {
    console.log("archived:", t.getFirstMessageSubject(), t.getLastMessageDate()); 
    t.moveToArchive();
  })
  console.log("finished.");
}