A few HND data points:
7/31 - Lots of lockers available in T2 early morning. Prior to the bag storage counter opening. Bags stayed in lockers until 8/6, counter to signs saying removed after 3 days...
8/6 - Only a few small sized lockers available in T3 around 1pm. A few seemed to have been occupied for a while as they had balances 4k+ displayed. Did not check the counter.