And while we are at it, on the gdrive side, I use a https://script.google.com to remove the oldest ones:
function FindEmptyFolders()
{
  var pageSize = 200;
  var folders = null;
  var token = null;
  var i = null;
  var thefolder_name = 'backup';
  var DeleteLimit = new Date().getTime() - 3600 * 1000 * 24 * 14;
  
  Logger.clear()
  
  var folders = DriveApp.getFoldersByName(thefolder_name);
  while (folders.hasNext()) {
    var folder = folders.next();
    // http://stackoverflow.com/questions/25749906/permanently-delete-file-from-google-drive
    var files = folder.getFiles();
    while (files.hasNext()) {
      var file = files.next();
      if (file.getDateCreated().getTime() < DeleteLimit) {
        Logger.log(file.getName());
        Drive.Files.remove(file.getId());
      }
    }
  } 
  MailApp.sendEmail('myemail@gmail.com', 'Old backups script removal', Logger.getLog());
} 
This one removes backups older than:
  var DeleteLimit = new Date().getTime() - 3600 * 1000 * 24 * 14;
hmm... 2 weeks I'd say (3600  1000  24 is a day worth of milliseconds, and the 14 would be the number of days).