I also got annoyed the one time that I got a box with only 4 products to review (it was the Davine's box in June -- THREE separately reviewable products that counted as one). Then I realized that I was being annoyed over $1 worth of points, and that I'd wasted more than $1 of my time being annoyed about it, so that was that for me. I might have felt differently if I was just getting a last box to "top off" points to get to an even $$ amount, but if you are planning to stay subscribed, I bet it will even out over time. I did get a 6 item box a couple of months later.
BB says that you get 40 - 60 points a month for reviews, and I know I've reviewed tea and a pen for points, so I am pretty sure that if there are only 3 "reviewable items" in any boxes in addition to the Chapstick that we will be able to review the Chapstick to get 40 points.
The idea to get 50 points a month for reviewing all of the products in your box is a good one, as it might take some of the "sting" out of getting a 4 product box (or 2 4 product boxes ... ugh!). Strangely, aside from the Davine's stuff -- which was too heavy for my baby-fine hair -- I really loved the other 3 items in my box that month and it was one of my favorites.