Is there a rhythm or schedule for when they do a stubs or pack sale? Thanks.
No real schedule. They usually have 4 or so stub sales every year and a few pack sales.
What is certain, though, is that a stub sale will occur with 12 hours of you buying some and same with pack sales
Only one that's "permanently" scheduled is the Black Friday sale.
The others I'm assuming are based on an algorithm that kicks in when money supply and velocity reach pre-determined levels.