OK, I'm sure I'm not the only one to have experienced this; in fact I'm sure there must be a writeup on this under some other name I have not been able to find.
This is about what I'll henceforth refer to as 'The Everything Head Rush Effect'.
I find this occurs to me almost every time I get up after an hour or so of random node-lurking; I feel as if I'd just crammed so much information into my head that I'm left completely mind-numb.
For some reason, I find this kind of cool, actually. I am quite sure all of the data I absorb at each sitdown eventually settles itself into place, opening new neural pathways and filling random knowledge/understanding holes all over my brain.