I spent a while improving this script for the Kindle PW2 - Better consistency of hitting the schedule, and much improved power management.
I was having issues with Kuhno92's version (high power consumption) and 64bits fork (wouldn't keep schedule) - This version fixes both of those issues.
This should work on almost all supported kindles (it tries to detect which power management process to use) but I've only tested it on PW2, so add an issue if it's failing on your device.
If you try it out, let me know how you get on
Link:
https://github.com/avhm/onlinescreensaverPW2