Do you normally turn the heat off and on during the day? I leave mine on all the time, with a thermostat of course.
It would probably be worth it to invest in a timer.
http://www.petco.com/product/119655/Zoo-Med-Repticare-Day-Night-Timer.aspx?CoreCat=OnSiteSearch
That one is usually about $20 at petco.
There's also one that is about $5 cheaper with only one outlet I think.
I would buy a timer from Walmart or a home store like HD or Lowes instead, much cheaper, I think about $7-8 instead of $20