@IxnayBob: In additional to financial aid concerns, the other reason to hold off on accepting Yale’s SCEA offer immediately is that a student might change their mind about which college they really want to attend AFTER they have received their RD notices. To quote Jeffrey Brenzel, recently retired dean of Yale Admissions: http://admissions.yale.edu/after-colleges-accept-you
Yale is a wonderful college. My son graduated from Yale and love it there, but the school is not for everyone and a 17-18 year old should take their time and consider all offers that are on the table before making one of the biggest decisions of their life.