Hello Redshift48,
The changes you made should be maintained after powering the camera off. The default settings for Auto power off and Display off should be 1 min, while Viewfinder off is 3 min. I would suggest resetting the camera to default settings and starting there. You can save the current camera settings to a memory card prior to resetting the camera if you would like to. That option is in the yellow Tools (wrench) menu #5. The camera needs to be in a Creative mode such as P, Av, Tv, or M to access all of the menu items. You can find the reset in the yellow Wrench Menu #5. There is also the Clear customized settings Menu item in orange camera #3 menu. Doing both of these will reset the camera to default settings.
