Generally a couple minutes- if I forget something or need to look something up (for instance iter_swap() I looked up yesterday- and managed to corrupt my heap with it in combination with pop_back() in a vector) But I don't spend any more time learning c++ itself, Other libraries on the other hand, more time than I care to mention.
14 hours a week, 2 hours a day from 10pm to midnight every night. You never stop learning C++ as there is always better ways to be found on how to do things. If you think you know C++ language then it is time to start learning other things like building complex software, libraries, game engines, etc. With as huge as the base is for C++ you can go into any thing to learn more (socket programming, driver development, making your own SDKs, etc).
I've stayed relatively up to date on what's been cooking with the C++11 standard, so there isn't really much more to learn in terms of language features. I can by no means recite the ISO paper by heart (nor have I read it in any detail), but most of the time now I spend on learning new idioms. Over the past month, I've dived into the boost::asio internals to see what's to learn from it.
Although, like many others here, I no longer study the syntax of C++; I have recently started running my code through OllyDbg in order to see how some of my more common operations get reduced and spit out. I can tell you that this can be some what heartbreaking to see what I thought was a function clever enough to deserve it's own header become reduced to "Why didn't you just do this JackA--?" by the compiler. And even though this is by far the most tedious and frustrating thing that has ever managed to hold my interest I feel like it's beneficial overall. So in this way I guess I spend about an hour or so each day learning new things about C\C++ and Assembly. Don't do this if you are a beginner, it will ruin the hobby for you.