I'll say that during my first round of NBE I had noticed a serious decrease in performance and function. After taking an extended break (not really sure how long) and after being back on I have not noticed the same effect. Only difference is that I'm not taking nearly as much SP and spearmint as I was before, but still taking between 1500 and 2500 PM daily. Even with this my breasts are still tender and growing, so from my experience it really depends on what combination of herbs you are using, dosage and how your body reacts to it all.
Regardless, even before I started NBE my boy parts were not functioning like they were 20+ years ago!