I used to always piece together fabric for the backing of my quilts and just hated having those seams.
Then....I discovered that fabric is available in widths up to 108"! WooHoo! JoAnn Fabrics also has a few bolts of fabric available in this width. It's great to use some of those 40-50% coupons on, when you can't think of anything else to buy. I buy the 108" fabric in multiples of 2-1/2 yards to keep on hand. Many of the most boring looking fabrics actually look very nice as the backing for a quilt. I try to keep lots of tan florals, black/white prints, blues, pinks and purples on hand. I would much rather pay a little bit of extra money for the wider fabric, than have a seam on the back side of my quilt.