Freshly ground bark seems to be best
You got it... This quote always stuck in my head,
One thing about distilling from root bark is that it needs to be done when the rootbark is still fresh out of the ground. Sassafras oil can evaporate into the atmosphere from the bark over time; this is what makes an essential oil different from, say, a cooking oil. The oil content of a dead tree is significantly lower than that of a healthy living one.
Post 336702 (https://www.thevespiary.org/talk/index.php?topic=9157.msg33670200#msg33670200)
(goiterjoe: "pretty small scale", Methods Discourse)