As a matter of fact, if you don’t touch your Kindle for several minutes, it will automatically go into the “Sleep” mode, just like most computers do. I’ve heard that, since Kindle uses the E-ink technology, it only consume electricity when you turn pages, transfer files, turn it on/off etc. When you read a particular page, unless the wireless is on, it doesn’t use the battery.
I’ve read some Kindle forum postings and found most people agree that it’d be better to let the Kinlde “sleep” than regularly turning it on and off.
But I’m still not convinced, so I emailed the Kindle customer service and below is their answer:
When you’re not using Kindle, it will automatically enter sleep mode. Unless you are storing your Kindle longer than a few days, turning it off is not necessary.
Therefore, from now on, I will not regularly turn my kindle off but just let it sleep. However, I’d remember to turn the wireless off when not using it for a while (such as overnight) because the wireless signal might drain the battery.