A quilt, even a top, is only as old as the last work done on it, so when you 'finish' them, they will forevermore be dated as 2011 quilts, not 1920-whatever.
Chances are, it will last longer as a vertically displayed top than as a finished quilt being used, even as a flat lying display on an unused bed collecting dust and such. The owner may get to enjoy it, but odds are her great-grandchildren won't be so lucky.