Albert Einstein is claimed to once have said that he keeps nothing in his mind that can be easily retrieved from paper – or looked up.
As far as I’m concerned, you should not memorize most things but instead memorize where and how to quickly find the required information and how to use it. Also, honing problem solving and analytical thinking skills is a better use of time in my opinion.
Of course it is a prerequisite that you understand the information and the system you are using, but not all details needs to be rote memorized.