iPhone battery life

I wanted to know if leaving the Bluetooth setting On all the time was an extra drain on battery life, even if the BT earpiece was turned off. According to Apple, it's a small tax on the battery, but many user comments on the forums I read (and my own personal experience) was to the contrary. Regardless, this is a useful article-

"Paying attention to just a few commonsense pointers will pay off with a longer battery lifespan and battery life for your iPhone. The most important thing is to keep your iPhone out of the sun or a hot car (including the glove box). Heat will degrade your battery’s performance the most."

-From Apple's iPhone battery info page.