Noticed that it's about 43 hours or so before a flight that is WIDE open in C (e.g. EF shows 7+ seats seat map shows 11+ unassigned) for upgrades seats in C to release. Don't know about the free bucket as it looks like all the people on the list were mile upgrades - had a co-worker who is HIGH 12 month rolling ($30K) and didn't get a comp upgrade - I did with a mileage one and I'm half his spend right now. Noticed the same 43 hours or so on other flights before and after mine. YMMV

Booked 8/9
Travel: 8/21
Route: LAX-JFK
Upgrade C class release: 8/19 ~ 43 hours or so - confirmed shortly after