I buy bags of logs from Academy or HEB for big cooks on the offset, either pecan, oak, hickory or mesquite depending on my mood and what I'm cooking. I cut chunks off of the smaller logs for the WSMs. I still have about half a bag of pecan chunks I got with the first WSM I bought off of Craigslist. If I run out, there's lots of oak in the firewood stacks.
BBQ Apprentice - Old Country Brazos offset, 22.5 WSM, Various gassers, portable grills, etc.