I listen to subliminals approximately 17-20 hours a day. Generally when I have traveled I have been able to listen probably 12-18 hours a day depending on circumstances.
Recently I decided to experiment with simply giving myself a break from the subs while traveling. Around Christmas I took a trip and had a full 10 days without listening to subs at all. This weekend I will not listen on my trip. One thing about these listening gaps is that they are irregular. There is no regular pattern. Also, I can easily set my listening up again so that I can listen almost as much as I normally would when I go on a trip.
I have no broad sweeping generalizations to make about this, nor have I really noticed anything out of the ordinary when I resume my conventional listening patterns.