My son had one at 7 months old, he's now 3 1/2 and I've recently discovered a " groove " in his head near the scar.
Only found it as he had a bump on the top of his head so was checking his out in depth and discovered this.
If you push hard enough it almost feels like a gap between 2 pieces of bone but isn't soft in the muddle if that makes sense?
Not sure I'm making sense at all and no idea what's normal this long on, certainly wasn't given any information about it and google is terrifying me