Every time I have found myself in this situation though, I end up in the docs. Just about everytime I'm in the docs poking around I tend to remember something I wanted to look up, or happen to read an entry I haven't seen before. I seem to always learn/refresh something during these times, which is always a good thing.

I think professional programmers should expect to spend %x percent of their time on improving their knowlege of their tools and %y percent of their time improving the tools themselves. Even under deadline. Insert x and y as appropriate for your situation; I like 10.