mmmm
Depends on what you want to learn...
I would think with (2) 5 to 10 hour sessions or less you could probably have a reasonably good understanding of how MIDI works... I'm not saying you'll have all the details - But, understanding communication through MIDI would get you a good start.
If you're talking about literally learning to 'play' a keyboard/piano - that could take some time... That depends on your own personal taste, capability and what you want to accomplish when you think you're "Ready for action"...
Further out then that is utilizing the interface of devices you're interested in using... That is no more than reading a bit of the manual and messing with their interfaces... Most (as a rule) handle MIDI in the same manner and those basic theories we just spoke of can translate to all hardware you'd be using...
There are also some of us that use the motto: "Never stop learning"
Start with some training to get your feet wet - Experiment on your own...
Eventually you may find that the basic stuff is pretty much under your belt... Then strike out on your own until you run up against something that you feel you want more training in...
You'll find as you start learning musical concepts and techniques for recording and playing your own instrument, theory, hardware, tehcnology advances, etc. you WILL INDEED 'never stop learning!'
Good luck....