Have you tried logging in remotely (say through a 'putty') and checked how much cpu is being used? The reason I ask is, when you open the gui on the phone it appears to awaken some processes.

For eg: I have only omweather and facebook widgets running. When I check using conky, I see a consistent 15-20% cpu use. When I remotely login and use 'top', I see a ~2-3% system usage.