I believe you really have 60 days, or the paperwork has to be redone. While the paperwork does state 7 days I believe, my guide said we had more time. We waited about 50 days I think to pay ours, as we were refinancing and I wanted that completed prior to doing the payment on my credit card. I didn't want that large sum to show on our credit report as havng any debt.
We added on at the end of September, to get the incentive, that is why we took the 50 days, instead of just waiting to add on in November.