Bought a pack of the First Response daily ovulation sticks today, because they seemed a bit of a steal (£30 for 20 sticks, rather than £20 for 7). But I've just read the instructions inside and it says that the sticks only 'last' for 30 days, after which time you have to chuck them in the bin. Now feeling quite , as there was no mention of this on the box (I know, I know, it did say they were designed to be used every day, but I thought I was being clever...). Anyway, I only need to use about 5 a month, so do I really need to throw the rest away?