Different strokes for different folks. I've got a bunch of LEGO Movie stuff sitting in front of my face nearly all day and I haven't gotten bored of the franchise at all. The story really spoke to me and everything about the movie has been extremely endearing. I'm super excited for the new wave of sets and happy to wait out the years to go until the sequel comes along. That's not at all to say that everyone should feel the same way as I do, but I've gotten the impression that a fair number of people are still interested in the movie, ergo there is a market for the new sets and film and what have you.

Think in terms of Toy Story 3 (I keep using it as an analogy for this movie, I should probably think of something else). It came out years after the first two films, but still drew in an audience and was by virtually any count a success. The trick isn't to keep people's interest over time, but to renew it when the proper time comes. It's a little early to say whether The LEGO Movie will have the cultural permanence that Toy Story has, but I think it is safe to say it has made a large enough impact to ensure there will be people to renew the interest of in 2017 (it was 2017, right? I don't remember).

I really should've put this up, but this is my opinion, so as you say it isn't everyones.

I agree that the 2015 sets are wholeheartedly unneeded, but, and this is coming from someone who initially HATED the idea of TLM, but after I saw it at that premiere, and got Benny's spaceship within 15 minutes of it's release at my store, I'd say TLM was really good, just as something to look at. I would never rewatch the lego movie by myself for its jokes, but I'd certainly watch it a few times at my computer just to pick up on small details I may have missed. In that way, its wonderful, and still retains tons of replay value. Also, having a bluray copy is good to bring to parties for anyone who hasn't seen it, and then like with any film, it becomes an experience in itself. I don't own all the Sherlocks on Bluray because I already know whodunit, i watch them over and over for the small details, and watch them with others to go through how well they hold up as flicks.

I've only seen it during the month it came out in theaters, and it still feels spoiled now due to it being plastered everywhere which helps maintain my memory of it. The novelty has been ruined.