On WN it is 4 hours prior to departure.
With the bad weather today, a supervisor needed to rebook a flight RDU - SLC. Because they had a 4 1/2 hour stop in BNA, the pax needed to collect her luggage at baggage claim, then recheck them herself at BNA to SLC.
I flew FL today. Checked my luggage 6 hours ahead of time and headed to the Club at RDU (old US Air/Delta lounge in Term 1).
The issue must be computer system related. Hope that WN changes their mind and adopts FL policy (and programming code).