I do kinda feel like my head is full! My context switching penalty is high and my process isolation is not what it used to be.
Frankly, though, I think most people can learn a lot more than they think they can. They sell themselves short without trying.
One bit of advice: it is important to view knowledge as sort of a semantic tree — make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to.