Google Apps Script to archive old emails in a label

GmailLabelArchive.gs

function shouldStop(startTime) {
	return new Date().getTime() - startTime.getTime() > 300000; // 5 minutes
}

function archive() {
	var days = 7; // How old a message must be to be archived
	var startTime = new Date();
	var date = new Date();
	date.setDate(date.getDate() - days);
	var label = GmailApp.getUserLabelByName("[LABEL NAME]");
	var threads = label.getThreads().filter(function (thread) {
		return !thread.isUnread() && thread.getLastMessageDate() < date;
	});
	var oldUnreadThreads = [];
	for (var i = 0; i < threads.length; i++) {
		var thread = threads[i];
		Logger.log(thread.getFirstMessageSubject());
		Logger.log(thread.getLastMessageDate());
		oldUnreadThreads.push(thread);
	}
	for (var i = 0; i < oldUnreadThreads.length / 100; i++) {
		if (shouldStop(startTime)) {
			Logger.log("Reached time limit, processed approximately" + i * 100 + " / " + threads.length + "threads");
			break;
		}
		GmailApp.moveThreadsToArchive(oldUnreadThreads.slice(i * 100, i * 100 + 99));
	}
}