Hello Walter
Hmm, that’s a difficult question to answer. Each lesson is different, and each person absorbs information at different rates and in different ways. If you are experienced in network technologies, studying for several months on an almost daily basis (1 to 2 hours a day?) may be enough, while others may need a couple of months of full time commitment to achieve it.
I suggest you start going through some of the lessons, maybe 8 to 10 lessons, and gauge how long it takes you to gain a full understanding for each lesson. Then you can estimate based on your progress, how long it will take you to go through the rest of the lessons. Only then will you be able to more fully understand what kind of time commitment you will need.
I hope this has been helpful!
Laz