We have a trip coming up in October. It will be the third trip for our son, who will be two months shy of 4 years old, to be exact. I measured him in February, and he was 39 1/4, so I assumed he'd hit that "magical" 40 inches by October. I haven't measured him lately, but I'm going to tonight! In the meantime, while I'm procrastinating at work, I was wondering what age other kids were when they were finally able to do those 40 inch rides. He really, really, really wants to do Splash this year!