Gotta be honest, but I can't believe that it's at all possible that directed study wouldn't be the fastest way to the top, just like it is for almost every skill activity there is. Obviously there is plenty of time to play 10-30 rounds per day and still study a little bit in the meantime. I just can't see any logical reason why boggle would somehow be an exception to the "studying helps a lot" rule.
I've seen massive improvements in my game in just the last few weeks IMO, mainly from studying some key word groups that there is no chance I would have known from simply playing. I'd have found them out eventually, but it doesn't seem like it hurt to have sped up the process. Also studying this game is exceptionally simple, much easier than poker, chess or anything else I've had to study.
Of course it's a lot less fun than just playing over and over though