Yes - agree with Fatdickie.

In my Silver days, I would set a calendar reminder in my phone, and would I often find they became available a little before T-72 hours. I usually made a "Book Row 1" appointment with the same time as the flights (but 3 days earlier of course!) and by default my phone would pop up a reminder 30 mins ahead of that (so T-72.5). I often found they were available at that point, so I don't think that it's to the minute, unlike e.g. free seat selecton for Bronze.