I thought I seen somewhere on the main site as to how long you should expect to spend on each lesson, but I can't seem to find it now.
Anyway, your question is sorta broad, in that there's no definitive answer, I don't think: it all depends.
It depends on where you're at right now. Are you an absolute beginner with no idea of how to hold a pick, or do you know the basics of how to hold the guitar, know what each hand does, but don't know any chords? Or, have you been playing for years (like I have), but never did it completely right?
I think that as you go to each Fundamental, you will probably know when to skip ahead over stuff you already know. BUT, be cautious: I have skipped over stuff I THOUGHT I knew, only to come back later out of curiosity and view the whole lesson, and find something I hadn't thought about before, that helped me.
In short, I would say there's no way to tell exactly. Just take your time and advance only when you've completely understood and can duplicate what the instructors are teaching.
Post back and let us know which stage you're at with the guitar right now. This will definitely get you some better replies. And stay tuned for followups by the masters.
Welcome to the site,
Terry