I must repeat this again - if you set up the autotimer correctly you should not have any repeats. However without knowing your settings there is nothing more I can suggest. You are correct in that you cannot disable the recording after it has started so it is best to avoid repeats in the first place. I have usually around 8-10 autotimers running - some daily & some weekly and never have any repeats.
If an autotimer is set to check the full 24 hour period of every day then you will definitely get repeats. Setting the appropriate time-spans gets the best results not concentrating on the exact title