Temps really helped me to figure out when I was going to be ovulating. I know that FF doesn't put a crosshair on until after 3 temp rises, which is 3 days after O (Really helpful!) but if you can see a sudden spike that sometimes helps, or if you know vaguely around what CD you will O you can be on the lookout and DTD just in case. Now that I've done it a couple of times I know that my O day is usually CD12, so I DTD from CD10 onwards.