What is shown a week out can and often has no indication of what will be available at check-in or day-of on many routes.

I've seen many, many flights that were J-9 a week out go to J-5 at T-48 and J-1 or J-0 at T-24.

J PAX, if they are paying full price, have a tendency to book at the last minute, then there are Bid-Upgrade, LMU's, SDC's, etc, etc, etc...if's very un-predictable.

I'm trying to SDC to a flight that was J-8 on Sunday, J-6 yesterday and is J-1 now without check-in even being open yet,

I'd say the best harbinger of an open J cabin is R>0 at T-7 days...they really don't think they are going to get any more for those seats when that happens.