Are STEM building kits worth it, or do kids lose interest after one build?

It depends on the kit. Reviewers praise replayable systems like Gravity Maze and the Klutz LEGO Gear Bots for repeat engagement, while single-build kits like the Smartivity sets deliver a satisfying multi-hour assembly but less long-term play. Build difficulty and instruction quality are the most-cited factors in whether a child sticks with it.