For me I can feel it when I'm getting burnout, some time better than others. Usually when I get burnout I go on vacation from the game, blogging as well because for me both are kinda linked together. Sometime I get tired of posting on the blog too because it takes time to do so. So I don't write anything for days, that annoys me more than not playing WoW.
But I go on my vacation from WoW and just not log in anymore for a while. I go do something else. For me it doesn't have to be more fun than WoW it just has to be anything other than anything related to WoW. Trying other games is good for a change of things. It would be nice if you could find a good alternative to WoW when you do as well get burned out.
I remember playing the WotLK Beta. After doing that and leveling to 80 in Beta and testing stuff I was burned out as well. Then all the constant nerfs just drove me up a wall. I wasn't having fun and I just left! I felt more like quitting the game at that point as well and did everything short of hitting delete on character. I gave away everything I had on my account and just quit playing for months. I went and did other RL stuff that was more important and needed to do. It was good to relax for a while. I slept better and had more energy as well. The break was good. In time WoW faded from daily thoughts for some time. After a long while it was nice to come back and play catchup but at my own pace. It was fun to start with not a single dime or anything in bank having to get things again.
Avoiding WoW was tough but it was good not to be focused on the game at all daily. I did miss reading blogs in that time. But I avoided that too just to be free of everything WoW related. But when you get burned out its good to go do something else or another hobby. Of course you can also stop playing your main character and just focus on playing a Alt as well for a change if you like that. But burnout happens often for all kind of reasons in WoW. When it happen just put up the vacation sign and take a break.
That reminds me I need to put in for my vacation time at work as well on the Job. I'm getting burned out on that too.