There's a good reason why it's not implemented: doing it the 'right' way would imply replicating the ads behaviour, and I have no idea how to do that, plus, it's not portable.
Doing it the bad way would make bypassing the ads trivial, so I won't do it either.
Plus, that would imply handling the 'device is asleep' issue, an issue which was tackled only very recently (
https://www.mobileread.com/forums/sho...d.php?t=236104).