I make alot of quilts that I like to use about 20 colors so for me 1 yard to 1/2 yards suits this purpose. But for a large scale print that screams border .. its 3 yards. If its just destined to be a great go to fabric for background say a white on white or cream on cream ... and it at a great price ... I go for at least 6- 7 yards , maybe the whole bolt ( if at a can't be beat price). For my style you can never have enough white on white or cream on cream on hand for me that like not having flour or sugar on hand.
So much depends on the styles of quilts that are your preference.