Need some opinions :)

What I'd do is swap around. Set yourself some sort of exp goal, like 2M exp in a skill over 99 and then 500k in one that isn't. Just arbitrary numbers, but that way it prevents you from getting bored as badly while still making progress. And then if you suddenly get the urge to finish off a 99, hey, all of a sudden those 5 levels you needed is only 2 or 3!

So basically what it sounds like you were already planning to do. Just don't try and think you need to rush all your skills to 99 for the sake of it. Keep everything fun.