As someone who's going to be Bronze for 3 out of 4 years in a row (with one solitary year as Silver), this has been by far the best benefit. Create a reminder on your phone at T-7 from the local departure time and select from there.
I've often noticed the map looks very different at that point compared to anything before it too. Flying back from JFK a couple of weeks ago and the seat map showed the upper deck completely full since booking. At T-7 I was able to snag 64K. Very glad I didn't stump up the £70/80 for a lower deck seat in advance.