instead of disabling cec another option could be to adjust the times that abm and epgimporter updates so they update at a time when the tv is normally on. I've had this happen before, on one box the tv came on in the morning while on the other box it didn't, it didn't happen then for a long while and then on the same box it started happening again, but not every morning. (or maybe I've not noticed it every morning). I like leaving hdmi-cec enabled so I only need to use one remote so never bothered disabling it.
In theory if the tv comes on during an update it should turn itself off again after, if it is then you could also mute the box before turning off at night, that way if the TV comes on it won't disturb you.