16 hours seems a little long..... I would verify your temperature and shoot for a slightly higher temperature like 250 to get the 1.5 hours per pound. Higher temperatures means an even shorter cook time.
Everyone has their own preferred cooking temperature, I've used 250° for over 20 years and it is second nature to me. I'm not willing to change at my age... don't fix what isn't broken. LOL
Humphrey's DownEast Beast W/BBQ Guru