Emma S, I would say it definitely works!
I'll often start thinking about backing before the quilt is done, but I tend to wait to buy backing fabric until I have the quilt top finished. Unless it's an obvious decision, like muslin backing, or a fabric within a single line I've used in the quilt, I usually take the finished top to the LQS and choose a backing there, or at least, get a firm idea of what direction to go in.