What I read is that we always have LH in our bodies, it is the surge we are looking for. This is why the second like has to be the same color as the test line or darker. In other words, you could have gotten a second faint pink line immediately and it still would not be a positive result. Also, I believe the test is void after 10 minutes.
It did say that some women (like myself) will get an increasingly dark second line and can tell in advance when they will ovulate and get the dark line. I tend to keep my sticks and use a permanent marker on them to remember which order I took them.