When do you stop pairing if you don't witness ovulation?

I'm in this position because I have two females who have not ovulated. I'm HORRIBLE at palpating and I don't have the touch to notice if/when they are reabsorbing. One was paired since October (with a move around January...but she's been showing building behavior since then) and the other has been paired since January. I don't wait to tire out my males because they are breeding endlessly if the girls aren't going to go but I also don't want to pull the males if the girls are just taking a little longer to ovulate.