Also, maybe selling excess cards to the store might also be a great idea to push through with credits. I'm out of credits, and it takes too long to level every unit to level 9. It would take even longer to bring it to level 10. Some units I have are well in excess of the required number of cards for them to level up, anywhere from 1.5 to 3 times the needed amount. I made a calculation long ago that if all the excess cards are sold, it could guarantee somewhere near 20K worth of credits if they were sold to the store for half the buying price.