Admin hasn't used it ,but believes it might not be related to the product, it could just be the natural fall and replenishment of your own lashes
Eyelash and Hair Growth
Although it may not seem like it, hair growth is a preset function of the body. Every hair on your body follows a specific growth cycle and will grow to a specific length. Hair follows a three-phase growth cycle and eventually falls out, which is typically nothing to worry about. In fact, body hair, including eyelashes, completely replaces itself every few years
Anagen (Growth) Phase
Also called the growth phase. This is the phase when lashes are actively growing, and it lasts between 30 and 45 days. Only about 40 percent of the upper lashes and 15 percent of the lower lashes are in the anagen phase at any one time. Each lash will grow to a specific length and then stop.
Catagen (Transition) Phase
Also known as the transition phase. During this phase, the lash stops growing and the hair follicle shrinks. If an eyelash falls out or is plucked out during this phase, it won't grow back right away because the follicle needs to complete the catagen phase before it can move on to the next one. This phase lasts between two and three weeks.
Telogen (Resting) Phase
Also referred to as the resting phase. This phase can last more than 100 days before the eyelash falls out and a new one begins to grow. Because each individual lash is in its own phase of the growing cycle, it's normal for a few lashes to fall out most days. It typically takes between four and eight weeks to fully replace an eyelash.
mismis agrees with Jen. Her understanding is that these drugs just increase the growing phase, resulting in longer lashes and believes it is too bad all Jen's are on the same schedule. In fact, hers also drop off, but never to the "stubby" point. She advises her to be patient and keep applying product. She also suggests it might be due to stress, to which djwar777 agrees.
Char_ has been on and off Careprost for about 2 years. She has also noticed what Jen describes. You get the first 6 months of great lashes, then the effect seems to slightly revert no matter how much of the product you use. She tried the tricks that people recommended: using less product and/or applying it less often etc. However nothing made a difference, but she still had the purple eyelid. She gave herself a break from Careprost for 6 months (and a month later she was back to her "normal" lashes. She took the break because it seemed it was no longer worth it, since her lashes were no longer fantastic, only slightly better than normal - yet the purple skin remained. She started up again that year and so far she has about 6 months of use and she can see the same effect again; longer lashes for a while, and then it's like there is a plateau (very common) and it slightly reverts back to the point where your lashes are "good-but-no-longer-spectacular"
Admin thinks it might be a good idea to stop using it periodically to get the maximum benefit, maybe using it in spring, so they're looking good in the summer and you could take a break in the winter
Char_believes bimatoprost extends the active growth window, and that's why the hair gets longer (because each hair has a longer opportunity to grow, time wise, before it falls out). She believes that even the so-so bimatoprost lashes are better than your natural lashes. If it wasn't for the red eyelid skin she gets, she would keep on going with the product