Can the back light stay on permanently? November 19, 2018 07:58 Updated Follow No, the back light cannot be set to stay on. The light will turn off automatically after 30 seconds from the last key press. Related articles Why does my heating come on when I don't expect it? How do Comfort Levels work ? Changing the Program Mode on your Slimline Thermostat Where can I download a manual for my Heatmiser Thermostat? Switching the neoStat to Timer mode