Our boys really enjoyed this toy, and were used extensively. A very good point for the robustness of the product, because our breakers irons have managed to break any mechanical element, despite countless shocks, falls, throws, and nights spent in the rain and frost!
We do not remember of particular concern in this balance bike mounting kit.
Finishes and mechanical side, there would be a few things to see.
Premature wear fixings "scratch" of foam protecting the front of the handlebar. One can foresee sew the heavy thread to hold them in place.
The fixing of the saddle is not perfect, always leaving a little turn the saddle on one of our bikes.
After a year, the presence of many rust on the sliding tube to get on and off the saddle. This does not harm security, but it's not aesthetics. Avoid leaving the bike outside moisture.
After 2 years of use on paved yard and paths, front and rear tires have become relatively smooth.
Not once our children have used the brakes. Maybe they are too hard?
And above all: the handlebar has always had the game, and increasingly with time. Even if the attachment still appears solid on our bikes. The system would benefit from being reviewed because it blurred the grindstone sense of security at night.
Think back to the seat when the child grows up (keep handy adjustment key), if not at home the edges of the shoes wear out strong rubbing on the floor.