Client connection test...
 

It would only take a simple 1 bit ping to see if a client is actually connected or disconnected because of a dialup connection being lost. Not to mention the idle time of 5 minutes can get annoying while waiting for a boat on GK. Some of them ferries take just about 4 minutes and if you miss you, you might as well get coffee. Yes, standing there for long times just to get your online time up isnt good. But honestly, what will someone gain by being online and not really playing, perhaps they went out to eat and forgot something was still connected (Graal). Perhaps you could reconsider some of your AFK and BRB options on Graal.

Are you suggesting idling shouldn't add to online time?
Or just that you should have more options for AFK/BRB as it takes too long to wait for the boats? The problem is, it is a bit realistic having to wait, as the boats go around the server, and the alternative would just be some animation that allowed you to get there and back striaght away - but it is better if you have to wait I think because then you can also go on the boat with friends and not get from one island to another when you want which would be unrealistic.

So... what are you actually suggesting?

Learn the dungeon routes then you'll have no waiting times to worry about.