I buy a lot of 1 yards and fat quarters. But I tend to like what I consider scrappier quilts.
If it is a backing or the main focus, I will get a bit more. But rarely have I gotten more than 4-5 yards. However, I just got to go to a textile factory sale to the public and got one cream and one mottled blue bolt -- 15 yards each. The prices were just too good not get something!
But generally I stick to one yard.