I finally finished this yesterday.
While I had a blast, I do think that that Luigi's Mansion 2 was right on the cusp of overstaying it's welcome. By the time I got to the Secret Mine (possibly even before then) I feel like I had seen everything the game had to offer. It's a damn charming game, it looks great, and Luigi is hilarious, but it was definitely beginning to lose momentum towards the end. It's for that reason that I'm kind of glad it ended when it did. An hour or two more and I probably would never have seen it through to the end.
*Also, was it just me or did this iteration of Mario look kind of creepy?