I have a mac mini:
Since my monitor doesn't play well with it, which takes a very long time to display correctly after system sleep, I changed the "Energy Saver" -> "turn display off after" to "never":
It works, but after I reboot my mac mini, it restores to default value (10 minutes):
Which is very boring, I have to adjust it every time when I reboot. How to make it always use the value I set?