I think (please note that this indicates the beginning of an opinion) that we worry so much about age appropriate-ness that we rather dumb our kids down in the name of being age sensitive.
The other day, Buddha was making a card for his Papa when he asked me, "Mom, if I'm trying to say, 'I love these and Dad too,' do I use T-W-O or T-O-O or T-O?" I was flabbergasted that he even knew to ask such a question at the age of five. I had given him this lesson ONCE, on a whim, a while ago. My thought at the time was that while he was showing a genuine interest in what I was saying, more information couldn't hurt and if he didn't get it, he could just grasp at whatever part of the lesson he did understand and discard the rest. But he didn't discard anything! His five-year-old brain filed the lesson away for later and LO AND BEHOLD there he was asking me, a few months down the road, which two/too/to he should be using in his sentence. Boy am I glad that I opted to give him more rather than less.
Isn't the human brain amazing?