title_body: Can the sleep timeout be adjusted on Kindle devices?
upvoted_answer: From the tags on this questions, I'll guess that you're talking about a Kindle Paperwhite. I know it's possible to do this on a Kindle Fire as well; it's in Settings > More > Display > Screen Timeout there (screenshots here).
  
  On the paperwhite, and apparently many of the other Touch devices, there are commands that you can input in the search bar to do all kinds of interesting things. Entering ~ds will cause the screensaver to never show. A full list of commands is available at http://wiki.mobileread.com/wiki/Kindle_Touch_Hacking#Search_Bar_Shortcuts
  
  EDIT: According to this forum post (same thread you linked in the comment, actually), it sounds like restarting the device is required to get the screensaver working again; the ~ds switch is apparently not a toggle. As far as power consumption goes, eInk only uses power to change the image, not to display it. This means that removing the screensaver may in fact extend the battery life, rather than draining it more quickly.