giftbox is a second inventory so its good for me
for me i usually use a date 29 per month to take it all

I cleared myself to expiry date 9 September about a week ago taking me to just under 100. I have something like 150 items, with 5 stages to clear in the event. Essentially, I just take Manyus out of a certain colour each day to fulfil the update quests (or Ampies when I have 10) and will keep overfilling the box until about the 7th, when I clear enough of the early stuff to be under 100. Note the expiry date of the earliest items, and repeat for next cycle