This is not allowed unless the unit you want is available at the 7 month mark. To switch the points, you would have to cancel the reservation and rebook. You would risk losing the reservation entirely, because it could be reserved by someone else, or could be taken to fill a waitlist spot. If you were willing to take this risk, I would suggest doing it late at night (like 3AM) so that there would not be many people online at the time.