You have to wait ZERO days to refinance or payoff the loan. As far as the DMV thing goes, most states give you 30 days to title.
For Example:
Oct 1: I go buy a new F150 and take the Finance rebate
Oct 2-10: I refiance and payoff Ford Credit loan, so new loan is with MY credit union.
Oct: 15-30: I now have 15 days to go to DMV and tell them the lien holder is MY credit union and title the truck.
This take a little more paperwork and hassle on your part, but well worth the $1000.
I don't know why they have that stupid Finance Rebate, I guess some people actually think they have to wait to refinance or payoff the loan.
It is that simple.