Not really much of an issue. In Metal Gear Solid V, a full day is 72 minutes. In Witcher 3, it's 90 minutes. It'd take a long battle to last longer than a day.
I really think the only obstacle is that it's difficult to make a living environment, which was essentially Larian's goal with the day/night cycle. People going to bed, etc.
Yeah; I think Oblivion's is one of the shorter days and even there it's 48 minutes by default (though I usually increase it to two hours or so). Changing schedules is nice but not essential: I like it when it happens in Oblivion etc but it doesn't bother me so much when NPCs have the same schedule 24 hours a day such as with Divine Divinity and Morrowind. The only thing I sometimes dislike is trying to find somewhere for my character to sleep once it starts to get dark!
