As I have witnessed the two boys in my life both being diagnosed at different times in their lives I feel that I am qualified to answer this question. In my opinion, I think that the age of diagnosis has a big impact on how well you 'deal' with it.
Let me start by telling you briefly about my husbands diagnosis. It was the beginning of January 1996, he was 24. He was a typical bloke, liked his beer and likes a fag. He still does, a little bit too much for my liking. Anyway he had been poorly for while, had lost lots of weight, was, tired, thirsty all the classic signs.It wasn't until his vision started to go that he began to think that there was actually something wrong. We had just registered at a new Dr's, so at our appointments, I mentioned my concerns to the Dr. To cut a long story short, his sugar levels were in the 30s and he was admitted to hospital, and there he stayed for two weeks.
He took the diagnosis very hard, and one to be honest I don't think he has ever really accepted , I don't think he ever will. At 25 years old you don't really want to be told what you can and can't do, what you can and can't eat, and what you can and can't drink.
Samuel on the other hand seems to be completely different. He was 4 1/2 when he was diagnosed. He was never actually admitted into hospital, as he never really got ill. We noticed on on the day that something was not quite right and we acted on it. Samuel is much more accepting of his diabetes, he just gets on with it, obviously he gets cross sometimes, and has days when he doesn't like being diabetic, but there are not too many of those days. Obviously, this wont always be the case, I am sure when he gets older he will rebel, he wouldn't be a normal teenager if he didn't. However, I will be ready for it! I have had enough practice with his dad!
So in answer to my question, I believe it does make a difference, I have seen it first hand. As much as it pains me to inject Samuel four times a day, I am pleased (if that's the correct word) that he has been diagnosed young, because lets face it, it won't remember living any other way!