You can control SteamVR device standby and headset screen standby with the standby_timeout_min and enable_screen_saver options respectively in C:/Users/[username]/AppData/Local/Pimax/runtime/profile.json.
Be sure to restart PiServiceLauncher (Start > Run > Enter services.msc > Right click PiServiceLauncher > Restart) after editing the file for the changes to take effect.
{
"Pimax P2 8K Formal" : {
...
},
"enable_screen_saver" : 0,
"standby_timeout_min" : 14400
}