I see where your coming from canadian cobra, but you just blindly say after 8-16 weeks i Must switch gears because that what im supposed to do.
Example: Say after 10 weeks he hasnt reached his bulking goals, it wouldnt make much sense to start cutting just because its good to alternate.
Ultimately i think this is an individual thing. If your a real skinny guy w/ a fast metabolism, you will be in bulking phase longer than say a guy who always has to lose a bit of fat or puts fat on easily. The latter will most likely be in a cutting plan most of the time.
But i can only advise from my expierances and from what i wintessed, that you should pick one or the other and focus on accomplishing goals for it. If you want to put on 20lbs. Focus on putting as much quality weight on as possible and strip away the fat later.