I have heard of something like this, from what I understand there is certain bacteria in urine, and the if it's held too long it can cause infections.
He's 7 months old? Hades was regularly holding it for around 8-10 hours everynight by that age. But he was let out quite often during the day.
If he's getting put out before you leave in the morning, once throughout the day and a few times when you get home he should be fine.
Some dogs are more prone to these sorts of infections, and a good diet can help solve a lot of problems
