From this post, Android disable screen timeout while app is running, I can disable screen timeout by
getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSC
Yes, that will work - it's how I do it in PocketSat3, though I don't toggle FLAG_FULLSCREEN (of course, that said - that app doesn't use FLAG_FULLSCREEN...)
Unlike using WakeLock, doing it this way doesn't require any permissions - though I have to admit it's not completely clear to me that is a Good Thing.