Seems like you and your son are doing great.
As you'll gather from many reports here and elsewhere, not every child wants to show what he knows. Many of us have had the experience of "catching" our children reading (when they are older than your child), only for the child to put the book down or do something else. From an early age, some children are just shy about this sort of thing. My own boy, now about 4.5 years old, can read newspapers and almost anything you put in front of him, and he continues to carry books around with him (as he has done since he was one year old) and flip through and read books for himself. But he does not like to read to me.
The ability to read at an early age is, I am convinced, a huge benefit. But it is not the biggest benefit you can give a child. Two benefits that are arguably even bigger are (1) a large vocabulary and large store of facts--and this is gained mainly by reading and discussing many books, and even more important, (2) true enthusiasm for and habits of learning. As many opponents of early learning are fond of pointing out, some of the world's great geniuses were late bloomers, and it is possible to learn a lot at a late date. Even if you did not start reading until age 8, as unschoolers have shown, it is possible to "catch up" and be doing advanced work within a few years. I don't disagree with this. The long-term goal is to have a person who is capable of learning a great deal, and who in the fullness of time, due to early training and habits,
does learn a great deal. (1) and (2) are the big keys to this aim, I feel.
I am saying all this because I would encourage you to approach your child's education as we did our first child's--we focused on making learning a positive experience, especially on reading a lot and doing whatever he wanted to do (education-wise). I didn't even learn about the whole early-reading phenomenon until mine was about 20 months old or so, and we didn't start in with my own flashcards (
http://www.mediafire.com/FleschCards) and YBCR until he was 22 months.
Frankly, here's how I see it. Suppose I taught my child to read at six months, and he was sounding out words at 18 months, and reading books independently at 2.5 years. If that same child were at age 7 nevertheless no farther along than his mother or I were in terms of intelligence and whatever might be relevant, if he was no brighter than we were, had just as large a vocabulary, read just as fast, and so forth, then I might want to concede sadly that all the time I spent on very early learning was a waste of time. But I don't think this is going to happen. I am very well convinced that, actually regardless of how he does compared to us or to other children,
he will have benefitted from training his neural pathways, getting reading skills and concepts as familiar as nursery rhymes, etc. He would have gotten this benefit even he never learned a single skill at a precocious age--was never an early reader, musical wunderkind, or whatever. In fact, even if someone is a very early reader or a musical wunderkind or what have you, it's still very much an open question whether the kid will grow up to be a scholar or a great musician or whatever. I think some people (not so many of
us, I think most of the people on BrillKids know better) want to see precociousness because they see that as something approaching a guarantee of future success. But, of course, there is no such thing.
Nobody likes to think of this as a race, but humor me for a moment and suppose that it
is a race. If so, what is the finish line? Or at what point, or points, should you determine success or failure? At age 14 months? Two years? Five years? Seven years? Eighteen years? 80? Say you found my discussion above persuasive, and you said, "By the age of seven, it should be clear whether my early education efforts were worth the time." Really? I wouldn't say so. First of all, the child's genius might still be dormant, so to speak. Even at that age, the child might have benefitted from early education--you just can't see the results so well. Second, a child might be wonderfully precocious at age 7, then have some bad experiences, and suddenly lose interest in school, and by age 18, be an ignoramus. I'm sure it's happened before. What's my point here? Well, it's simple: while you can measure how well a child (or any person) is doing against his age peers, this is not very meaningful because children are all different and there is always both opportunity and danger in the future. Moreover, it's impossible to determine how much better a child is doing as a result of going through some program, because you can't compare two different worlds. So, ultimately, we are stuck making reasonable guesses.
I think it is a very reasonable guess that exposing your child to many words in the way you have will ultimately make it a lot easier for the child to learn to read, when he is ready. This might be sooner than you think--if your child just doesn't want to share what he knows, there's no way you can elicit his full brilliance. You should take it easy anyway, because repeated experience of everyone shows that if you push a child much, he'll push back and dislike whatever you're pushing. Anyway, I'd say, as long as your child likes what you're doing, keep doing it. I'd also add that if you can find some other similar (but still different) activities that he likes even more, and seems to be getting more out of, try those--keep "changing it up" until you find exactly what works best at any given moment.
Descending soapbox...