As long as you remember your password, I'm pretty sure they'll still have your character on the server.  The only thing you'll lose will be preset things like macros you've set.  I was gone for like almost a year and then came back and Tevyn was still there, Quin.  Twice.  
 
It's probably because they don't have a huge influx of new people coming in and so there's more room or memory to keep characters on there?  I guess in all seriousness, they 
could get rid of your character if you were logged out for like 3 months if they needed the memory.