Before LCD screens appeared we used to have screen-savers protecting our monitors. Modern monitors are not in danger of burnings, so that a screen-saver may shorten their life rather than increase it.

If you want to make sure your monitor lasts as long as it can, just turn it off when you don’t need it.

You can choose a power scheme in Windows, if you prefer, to have the system activate the power-save mode automatically after a period of inactivity,

or even better use Sleeper or NumPad Transformer to activate power-save mode whenever you want it, with your keyboard.