At 8 weeks old he can only hold it for about 2 or 3 hours... he needs to go out every 2 or 3 hours regardless of time of day, just part of nature. Can you hire someone to come over while you are at work or a neighbor let him out?
he should also go out 15 mins after eating and right after any play-time. Good rule of thumb while training is 1 hour more than months old is all they can hold it. so, they can not go 8 hours until they are about 7- 8 months old.