Size makes more of a difference if the quilt is hung 24/7/365. If it's securely and evenly supported when hung, and given occasional time to rest off the wall, there should be no problem no matter how large it is. Even small wall quilts, if hung incorrectly, can stretch and distort.
The MSU Quilt Index has some great info on quilt care.
http://museum.msu.edu/glqc/quiltcare.html
Applique may have some personal experience, too, from what her museum does.