Hi, the latest firmware 2.1.9(7) supports LED dimming. In fact, if you go to Edit Options -> Advanced -> LCD brightness, you can change that to 0, that way after 20 seconds of inactivity it will turn completely off. Pressing any button will activate the screen again. If you set the brightness to anything above 0 it will dim to that brightness after inactivity, but the difference may not be that obvious.
Besides, as you noticed, the OLED used on OpenSprinkler 3 is a very common inexpensive one that’s widely available for just a few bucks. So in the case the OLED burns out eventually, it’s fairly cheap to replace.