We are now about 18 months in and just decided to cancel it.

Initially our kids loved them, got into it. Had one box for the 4 kids, they all took turns building the steps and loved playing with the finished product. However, lately its become just another thing. The kids lose interest about half way through the build. On top of that the quality of the toys sucks, and this has become a pattern in the last 6 months. We had 3 of them that didn't even work remotely close to the way they should have worked. The kids are only into the build for about 3 days after, and then it ends up just as junk, many of them broke after a few weeks. We typically throw the last one out before we get the next one.

Should have stopped at 6 months.