I'm 18 years old the way that we currently measure time. If nothing changed other than 1 year being 730 days instead of 365 days, I'd be 9 years old. What I'm trying to say is that age and time are just a matter of perception.
I don't get this thread. It's not a matter of debate.
You would be old as your clandestine age, you just wouldn't be aware of how old you are. Not knowing your age doesn't change the factor of how old you actually are.
Being a infant and not knowing how old you were age didn't matter. So if age is an unknown number you are living a infinite possibility of different ages and thus you are immortal in your own eyes.