I think if the results you are looking for are looking and feeling healthier, 21 days is probably enough time to see them. When you are close to a healthy weight for your height, the weight loss results may very well take longer. I am 2 lbs from my official goal and probably 12 from my optimal goal and I fully expect that these last few lbs will take as long as the 1st 60. I'm OK with that because I feel amazing and I don't stress over the non-primal stuff that pops up.
I think too, that as you get closer to an ideal body weight, the sleep, stress reduction and physical training aspect of PB becomes more and more important.
CW-125, part calorie counting, part transition to primal
GW- Goals are no longer weight-related