I'm using Android V4.4.4 on a Moto G from Republic and Screeble lite 3.0.50
Like many others, I find Screeble constantly getting disabled. After doing a little experimentation, I found the problem is related to Display Sleep setting and Google Apps.
Chrome is the worst, disabling Screeble and putting the phone to sleep as soon as the Display Sleep time is reached. It won't even go to daydream.
Google Maps is bad, too. Possible Google Books too.
With other apps, the screen dims after the Display Sleep timeout, then brightens, but at least won't shut down on me.
Since Display Sleep cannot be disabled, the best I could do is to set it to the maximum, 30 min. Then I only have to go into Screeble and turn it on again every half hour when using those Google Apps.