I would think that either:

1) The quantities of copulins change over the ovulation cycle (same mix, different total amount)

OR

2) The quality (chemical composition) of \"copulins\" vary (different composition and maybe total varies too)

Either way, the effect on males is shown to track ovulation. I would suspect that ovulation causes qualitiative changes ( #2) and would hope that manufacturers mimic that ovulation mix. But, given my experience with a variety of females, the precise composition of copulins probably varies between individuals as well as with time.