Mine has kept some and discarded some of that early-memorized knowledge. It surprises me how much he's retained: he will come out with the Latin name of a cloud formation (learned at age 5) or the surface temperature of a planet (age 3) and it will certainly take me back to those days.
He increasingly is able to use his accumulated data as a reference library (i.e. knowing the whole periodic table by heart really does help you do chemistry faster). I'm glad he's integrating the information...
DeeDee
