Ah. Interesting. I wondered if they might do that. Since the LKS needs to be a snug fit in order to be effective, the toddler versions can only be worn for a relatively short period before the child simply outgrows them, so engineering for longevity is not really a consideration. Obviously that isn't true of the larger sizes, and fabric that is near-skintight is placed under more stress than something loose. Thicker fabric and stronger seams would make sense. I would have actually expected them to re-engineer the adult versions sooner, but I'm getting the impression that they receive large batches of stock at very infrequent intervals.