When we towed, 12 hours was the max in one day, 8 hours to 10 hours a day was normal.  If you have never towed long distance before, you might find that you can't drive as long per day as when not towing.  You have to be more attentive when towing and it can be stressful.  If your Tow Vehicle doesn't tow well or your weight distribution/sway control are not setup properly, you may find towing to be difficult.  You don't want to rush it when towing.
I would estimate 2 days for the travel and add an extra day just in case.  If there isn't a penalty for getting there early, maybe add 2 extra days just in case.
-Michael