Why push it? Just apply for the checking account now. The official language is a little unclear, but it may already be too late. This is the wording straight from the Chase website:

Chase Exclusives® Bonus: You will earn an additional 10% Bonus on all new points earned with your Chase Freedom card during billing cycles within the previous Year when you, as the primary cardmember, were the sole or joint owner of an open Chase checking account. Your 10% Bonus is calculated after your billing cycle with a December closing date ("Year" means the twelve billing cycle period beginning the day after your billing cycle with a December closing date through your billing cycle with a December closing date of the next year.) Your Chase checking account must be open, and your Chase Freedom card account must be open and not in default, at the end of the Year. Your 10% Bonus points will appear on your January or February billing statement. You will not earn the 10% Bonus on new account bonus points, previous 10% Bonus points awarded, or points transferred into your account. You will earn on other bonus offers, including the quarterly 5% cash back program. Bonus offer void where prohibited by law.