In many cases less time that what I spend looking it up. I regularly look up things I haven't needed before, a few minutes of reading and I know it. Many of those things are something I expect to never need again in my lifetime. The few seconds to memorize all those things is greater than the time saved. Particularly since I don't know what I will need next week and so I'll be spending a lot of time learning things I turn out to never need.
