It depends on the dog.
A significant number of adult dogs at rescues are there because they need more human contact than their original owners were able to give.
The first consideration is a physical one: can he comfortably go that long without relieving himself? Just because a dog doesn't have accidents doesn't mean he is comfortable. If he needs to race out to pee as soon as you get home, or if he has a very hard belly, the long indoor day may be causing him physical discomfort.
The second consideration has to do with the environment. Is it comfortable, peaceful, and mostly stress-free? Dogs who are calm and balanced when their people are home may become anxious and agitated over things like doorbell ringing, construction noises, neighbors in an apartment hall, or sirens from trucks leaving a nearby fire station.
Also, even though he isn't destructive, is the environment fairly well dog-proofed to prevent common problems? Examples include: only non-toxic house plants, lidded trash can, no food/medications/sweets left out on counters or table, etc.
The third consideration has to do with his temperament. Does he seem content when home alone? Anxious? Depressed?
There are some dogs who will peacefully work through a loaded Kong toy and settle in for a nap in their comfy bed, confident that their owner will be home in time. And, there are some dogs who fret and worry all day; they are inherently pack animals, so being all alone is stress inducing for some.
I love the inexpensive surveillance cameras that you can link to your phone these days - it is an amazing way to know what is going on when you aren't home. You can even turn an old phone or ipod into a security camera, linked to your current phone.
Hopefully, you'll confirm that your dog is comfortable and relaxed.
If you see signs of anxiety, however, you might consider having a professional dog walker stop in once a day. A high quality dog daycare is an option for a social dog, or get creative with possible solutions. Family members might rotate dog walk-lunch breaks into their routine. One friend of ours drops her dog off with the elderly neighbor each day. She pays a small amount for "babysitting" and the neighbor enjoys the company. If your dog is VERY easy going and well trained, and you have a fenced yard, you might pay a neighbor kid (9 and up) a small fee to take the dog out for a game of fetch right after school each day.
The trick is to individualize to meet the needs of your unique dog, in your unique situation!