Just finished The LEGO Movie Videogame. It took me just over 30 hours of gameplay to reach 100% completion.
As impressed as I am by how quickly I was able to complete this game, I have a feeling it'll turn out to be more of an exception. First of all, I had already completed this game multiple times, so I already knew where to go and what to do for everything. Second, based on the glimpses I've had of many of the other Lego games, this one appears to be rather small and simple by comparison, so it will likely take me a longer amount of gameplay time to complete the other games. Finally, I had done this game by playing an average of three or four hours each day for ten days and was able to spare time for almost every day of the week to do that, but once I get to the other games, I seriously doubt I'll be able to frequently spare that much time, so it's possible it could take me well over a month to complete each of these Lego games.
I'll wait until January before I get started on any of the other Lego games, since there's a chance that I'll be quite busy with other things next month.