Hi JBDad,
Do you think there's an age component too? For instance, a lot of stuff DS6 (almost 7 now) did previously (ages 4 & 5) math topics, books, poems, tales, etc. peaked his interest then & we discussed them and he loved it. Switch to age 6 and he has almost no memory of much of it. He picks it up quickly once it's re-introduced. Guess we all are a bit that way, but usually my lapses are things I learned 30 yrs ago rather than just 2 yrs ago.
Interesting that you had a similar experience. We're still trying to figure out our little guy. When we first started to notice that he might be gifted, he seemed to learn things at an unbelievable rate (age 4 3/4 to 5 1/4). He'd go really deep on a given subject... what appeared to be very "vertical" interests. He still does that to a degree but now we do notice that he goes a lot more broad on his interests. More "horizontal" learning if you will.
It's interesting to think that this might be age related. He's got the mechanics of reading and math down, but there is so much more to learn about life sciences, geography, or history that he's been digging into those topics lately. Didn't think about that.
JB