4 is the most i would go. simply because users have great results @ 2 caps, so I would not see the need to go above 4. The ingredients are natural, however what we're concerned about is not actual side effects but a pleatau of effectiveness like you said.
3-4 caps is the highest I would go. That way you can make the bottle last longer while reaping the rewards.
Any thoughts of instead of taking a high dose of Blue Up, try stacking it with Blue GENE. It works through a whole different path way and therefor blends quite nicely.
RR