I think as long as it has 8 hours on low - or 4 on high, it really doesn't matter
if it goes over the 8 hours. (ie: start it at 8am and eat at 6:30pm) - I've done that more often than anything because that's what my schedule allows for. But sometimes, I don't get around to starting it until noontime, then I just set it on high and let it cook for 4 hours, then ...
if I remember,... I turn it to low after the first 4 hours until I'm ready to have dinner)
I usually do a pot roast and use the crockpot seasoning mix that you get in the seasoning aisle at the store. They have a good one that I like to use. Then you don't have to do that can of soup stuff (and can avoid the milk)