At the start of my last cycle (Oct 31) I went to Walmart and picked up a 20-pack of Answer OPKs. I started using them right away and always got a second line, ranging from light to dark, but never as dark as the control strip. That cycle ended up being VERY long so I gave up on the OPKs and never did see whether or not I would get a positive result with them. (My O varies by weeks from cycle to cycle) So, fast forward to current cycle and I've started using them again, but now I'm not getting any test line whatsoever, although the control line looks fine. I didn't think much of it but I was just re-reading the directions, and notice that it says all over the place to use them up within 30 days of opening the package. It's certainly been more than 30 days since I opened it; closer to 90. I Googled it a little bit and most people seem to say that they're just trying to rip you off, or that if they didn't work that the control line wouldn't show up. My control line shows up fine, I'm just not getting any test line at all...and that may even be normal as I don't think I'm approaching O quite yet. I've already ordered more OPKs and they should be here in a few days, but I was just curious if anyone had any experience with these and knew whether or not they really don't work after 30 days, and if not, what happens? I thought maybe that was the reason I stopped even seeing faint lines.