My first dog was pretty young when we started leaving him out all day (Less than 6 months) and he never had accidents. My other two were much older. Roo is going on 4 and I've just started leaving him in the house loose this past summer, he probably would've been fine earlier but I was renting and didn't want to risk it. Newest pup is 14 months and she's not ready. She can hold it the full 12 hours in a crate except for when she can't.. over night has been no problem for awhile tho and she is loose now. I think the big difference in my two younger verses my first dog is that my work day is so long now (12 hours) that I never liked leaving them in a crate that long so they had a kennel set up where they could potty so they never had to learn to hold it all day. Even at night the past few years I had a senior dog on meds that made him have to pee often so everyone got potty breaks several times throughout the night.