I would definitely look at getting 2 dogs of whatever breed you end up getting (if at all) I know some people do work long full time hours and still have a dog, but in my opinion 8 hours is WAY too long to leave any breed of dog on its own, it must be boring and lonely if a sole dog is left for that long on their own even if you pop back at lunchtime. No offence to people that have to do it, and if you have a dog that has adapted to it then great, but what dog would choose to be on their own for that long....
good luck with whatever you decide
