davemoog, my Werkstatt is in a room with pretty stable temperature, but I noticed that it stabilized pretty quickly (maybe just a few minutes?) and stayed there over time. However, it never had to deal with large room temperature fluctuations.
Frequency was evaluated by comparison to a quartz oscillator.
I completely agree that the tuning knob is way too small and wide-ranging to accurately set the pitch. I did two things: Added a larger knob over the shaft. Added a fine tune pot (internal) wired up as in the Werkstatt Workshop video.http://www.werkstattworkshop.com/?q=projects/fine-tune