If you don't see a
Code:
Using user specified timeout 1800 from /mnt/us/screensaver-timeout
line in your install log, then you misspelled or misplaced the 'screensaver-timeout' file. (It should be in the root of the Kindle, and without any file extension (ie. 'screensaver-timeout' and not 'screensaver-timeout.txt' !).