The way this works atm is that despite it showing you that the travel time is, for example, 135 minutes for Bareshade, if your horse has energy then the time it takes for you to reach Bareshade will in fact be reduced. You can confirm this fact by checking the little time display at the bottom and seeing how much time actually passes when you travel from your home to Bareshade.
Oh, Okay, I get i now. But still sucks. Hopefully the Travel Time for mounts will updated soon. Or an addition/replacement, a Clock on the map section when the Player arrives at a certain Location. Also viewable Energy Stats for a mount at Main HUD when traveling so the Player would know how much energy there is left from the Mount.