gmailAutoArchive.js

function gmailAutoarchive() {
  const delayDays = 2;
  const batchSize = 100;
  
  const maxDate = new Date();
  maxDate.setDate(maxDate.getDate() - delayDays);

  const threads = GmailApp.search(`in:inbox has:userlabels older_than:${delayDays}d`).filter((thread) => thread.getLastMessageDate() < maxDate);
  
  if (threads.length) {
    Logger.log(`Found ${threads.length} threads:`);
    for(var i = 0; i < threads.length; i++) {
      Logger.log(`  ${i+1}: "${threads[i].getFirstMessageSubject()}"`);
    }
    
    while (threads.length) {
      var batch = threads.splice(0, Math.min(threads.length, batchSize));
      
      GmailApp.moveThreadsToArchive(batch);
    }
  } else {
    Logger.log(`No threads to archive`);
  }
}