I agree, GPhiBLtColonel. If sisterhood is supposed to be for a lifetime, then nonfreshmen should be considered on par with freshmen. There is no guarantee that all freshmen will be around for 4 years, but the odds are better and I understand that. I would much rather find the best members/representatives/future supporters of my GLO, whatever their year, than just look at freshmen.
I guess it boils down to numbers. When a PNM is expected to be around for only 2 years as opposed to 4, then your GLO will graduate more members sooner . . . unless you replace the ones graduating with nonfreshmen!