This is the worst possible setup to print living hinges: PLA isn’t terribly flexible, and here the flexible bits have to be printed vertically, which really isn’t ideal to withstand cracking.
Yet when the application isn’t heavy-duty like in this clamp-on connector, even PLA printed “against the grain” works well too: this connector can spread its hooks linearly 3 mm apart and the living hinges don’t crack or weaken even after many cycles.
The toys held up under the abuse right? The toys?
At some point the toys would fail, they were 8 and 9 year olds after all, but it could take a month or more in the hands of children. I was pretty shocked. I did have a paper wad cannon that had a spring that was printed all in one inside the barrel. The first few had issues with the compression spring breaking when over compressed by the kids. But a bit of a redesign of the spring by making it beefier, it not only lasted nearly the whole school year but the kids got more range. Much to the other teachers and parents disappointment.