It's 9 hours. I work 11 hour days three days a week, 16 one day because of my volunteer (read experience)TV job. We do get a half day though.
Have they given you time to consider the offer? If so, do a little more research on the company. I've worked for a few unreputable companies before. He does have some legitimate reasons to be concerned. If the pay is good, take it, but go with caution. Besides, corporate loyalty is dead as SunnyD says. Too many jobs on a resume only looks bad if you get fired, or resign without anything else lined up. Besides, I've found you can put too much on a resume. Stick to what's relevant and always hold something back.