Just to report back: I checked my bags at the curb between 1230 and 100 for a 530 flight. No one batted an eye. The flight ended up being delayed until almost 7, and despite there being intervening flights, the bags flew with us. They were among the first bags off with the other SkyPriority bags. All in all, it was a great system I fully intend to utilize more when traveling with the family.