An option in the settings to declare how long the processor should stay active before slipping into sleep mode.
In this manner, say, you set it for 1 minute. If you take less than a minute to read the page, when you advance to the next page, it will turn just as fast as if you had changed pages in quick succession. If you take more than a minute, then changing pages will take the normal 1.2 seconds or so.
It shouldn't have too much of a drain on the page turns. But even if it dropped the pages down from 8000 to 4000, that's still a good 4-7 books before charging.