I have played this game on and off for about 10 years and I can't remember the maintenance time being accurate once. What bothers me more than them being awful at estimating downtime is their vague way of extending set downtime.
Any gaming company wether it's Riot or Blizzard will post on forums, website and social media how much extra downtime can be expected and makes sure that when they do so it's a promise they can keep because continuous disappoint sucks and they understand that.
Nexon however just gives us the most vague statement: "[Update] The maintenance has been extended until further notice."
Basically telling us to sit down and wait until they're done. 1. This doesn't tell the player ANYTHING. Can I expect another 5 hours downtime? Or are we talking an additional 30 minutes? 2. This kind of message makes the initial estimate completely worthless. Why bother giving the players an estimate when youre planning to extend it "until further notice". 3. In times they HAVE actually told us the extended downtime they usually start with an hour and add an additional hour everytime they pass it. This to me is extremely annoying because you get your hopes up and plan accordingly over and over.
Nexon needs to step their game up when it comes to maintenance and communicating with the public. Patches and updates should be exciting times but by the time they put a patch through everyone is usually pissed off by the way they handled it.