Do the results depend on the size of the lips to begin with?

I've seen a lot of good responses to this product and a lot of bad responses. Unless the people with the bad responses didn't follow the instructions correctly, could it not have worked for them because their lips were very thin to begin with, whereas the people with the good responses had more of a fullness to their lips to begin with?

On the before and after pictures it looks like the people with average sized lips got a lot better results than the ones with very thin lips.

I ordered this product (havn't gotten it yet) and i'm a bit discouraged from reading the bad responses. However, I already have somewhat full lips to begin with, so i'm hoping that if that does help, and if I follow the instructions very carefully, this product will give me a good result. Reassurance?

Also, do your lips really stay bigger over time?