Save your credits until the LAST DAY of the flights! You can use them to buy BP levels, the XP challenges will help you get pretty high up the BP, but when you’re stuck with none toward the end, you can cap it off with the complimentary credits! Let’s have this weekend (and next) and don’t forget to fill out those tickets!!
They should have fixed the challenges so that shouldn’t be needed this time around.
I’d recommend spending them however quickly you want, especially if there is something nice in the store!