The actual North Africa campaign lasted a little under three years, let’s round it to 150 weeks. So if you spend less than 10 hours a week playing CNA, your game will take longer than the actual military campaign.
I think a big part of the problem is that Campaign for North Africa is a badly designed wargame, in the sense that it's not abstracted enough.
One of its flaws is that it makes you, in the role of the commander (or one of five commanders, anyway), keep track of:
> "[If using the full rules] every individual plane and pilot in the three year campaign."
This is madness! A real commander wouldn't keep track of this, so why must the player? This level of zoom-in is typical of tactical wargames, where it makes sense, but it's nonsense for traditional "cardboard" grand strategy wargames without computer assistance. So it makes total sense that playing this would take more than the actual Campaign for North Africa, since in the real deal those commanders wouldn't track every individual plane.
I don't think this was made to be actually played, and I struggle to believe anyone has actually finished it, regardless of some internet claims.