Farming now or farming later

I'd recommend farming the petals now, because of the CE the boxes give. If you farm it now you'll be ready to beat the harder quests and then you'll have all the remaining time to empty the shop.
I'm farming mostly for the knight medals and QP tho, since emptying boxes is pretty quick; especially since we got 18 apples

I would farm medals right now (the preliminaries 10 AP for Bronze Medals and the 20 AP for Silver Medals are comically easy).