To reiterate and preface what Lyndsy (orginal poster) has said. This worked for us when L was around 10months or older, when her cues seemingly 'disappeared' and nap time was a disaster - lots of crying and frustration (by baby and mummy). I didn't know when I should be putting her to nap, and she was getting more frustrated and tired. This does by no means mean that I ignored her cues...so if she was really tired, then we put her to have a nap/bed. But I often missed the window and that made things even worse. Even now, going to one nap, if she is really showing tired signs then I respect that and start the sleep routine. I also think this really depends on the temperament of your child. Mine is textbook/angel, and loveeeessss routine. Thrives on it, but needs her sleep. I'm not sure it would work as well for a spirited and a touchy baby,because I have no experience with one. But when all else is failing, then you can try it.
I guess in the end, this is something that I tried, and works for my lo and my family. First and foremost, listen to your child, watch your child, and find the solution that works best for them.