My dogs spend about 4 hours at a time on their own while I am at work. This has been the pattern for about 25 years and has never been a problem.

 I've had dogs all my life, mostly big dogs too. German shepards, saint bernards, chows, akitas....
I personally think its cruel to leave them home alone longer than 4 hours.
Let me ask you this, would you like to be left completely alone 9-10 hours a day almost every day of the week? Or how do you think it would feel to not be able to go to the bathroom 9-10 hours a day almost every day of the week?
Would you like to be put in a crate with barely any room to stretch, play, eat, sleep for 9-10 hours a day?
Dogs are very social & extremely pleasing. You'll either end up with a sick dog all the time because they will try to please you by not having accidents all over the house
or you'll end up mad because you will be cleaning up accidents every day!
If you don't have the time to put into loving them, caring for them, and just having them as a best friend, i'd suggest get another type of pet.

 I don't think its wise to leave any animal for long periods of time, I only leave my dog for no longer than 2 hours a day .. How would you like being left alone with no way to eat drink or even most go POTTY? If you haven't the time to take care of their needs then maybe you should consider fish or something that doesn't need the required attention a dog does

 I dont think you should leave your dog home that long i kind of agree with sahm1 and jiggleypuff you wouldnt want anyone to leave you like that so maybe you shouldnt consider getting a dog if you cant handle that responsibility

 I have had dogs all my life from bull mastiffs to yorkshire terrriers and we have neveer left them at home for more than 4 hours........i kind of agree with sahm1 and jiggleypuf because you wouldnt want to stay home by yourself thatlong and ifyou cant handle that responsibility i dont think you should considergetting a dog right now

straight from atlanta

 I would say no longer than 8-9 hours..we leave our baby shar-pei in her crate for 8 1/2 hours and she doesn't seem to mind..she waits until we let her out before she potties..thank goodness!

 It depends what kinda' dog it is.i have labs,i leave them at home for two hours and they'll destroy the house because there big enough
two eat the bread off the counter,but they don't often chew on things.

 In my experience when I leave my dog for 2 hours, she gets panicking...

 I've had a yellow lab now for 3years. She is alone for 8-10 hours 5 days a week. She's fine. It's all in how you train from the start. Keep in mind if u get a puppy though; they will need to potty several times through out the day! I was fortunate enough to have a friend that lived nearby check on her while i was at work. I also "kennel trained". This means u put him/her in a kennel when you are away. They will learn not to go potty in it, because this is their "home". Allow yourself several months to get adjusted. Their WILL be plenty of "messes" to clean up! LOL! Now that my dog has matured, she has free rome of the house. I let her out b4 i leave and she's perfectly fine until i get home! I'd say it took me 6 months to a year before i could do that. It all depends on the breed and YOU! Dogs are wonderful! But i suggest doing some research on the different breeds and how to train them! They are worth the effort. A dog loves you ALWAYS and NO MATTER WHAT! Good luck!