Instead of moaning you can also see it form a positive perspective ; Maintenance is just a simple word for improving the gameplay. Developers are working to make the gameplay even more joyful for the MapleStory players. In those hours you have the time to do something else, think about playing a different game or do something in your real life. I suggest doing something with your real life since that's healthier than staring at your screen. Anyway, if there would have been maintenance everyday i could've understood the moaning, but moaning for just a 5 hour maintenance? No.
If you really want to stay in the MapleStory environment, even when there's maintenance, you can just go post on the forum.