Unfortunately the screensaver is re-enabled if the Kindle reboots. I was trying to use this to revive a Kindle 3 which had the power switch broken. The power switch only switches in and out of screen saver mode. Every time the Kindle resets – either due to the battery draining or a freeze up when browsing etc it re-enables the screen saver.
It would be necessary to either attach a start up script to the boot procedure or modify the boot procedure to ensure that the screen saver is not re-started.