QuiltingPandaBear

@KalamaQuilts your comment could not have come at a more crucial and helpful decision point!!!

I am working on a quilt at the moment. Top is nearly done and I was going the direction of making an “afterquilt” on the back, using up all the bobs and bits of leftover fabric. As I was making progress, doubts crept in:
(1) There is enough to make it a second quilt top (with considerable negative space, but I like that).
(2) extra seams on the back make it less cuddly/soft to use
(3) it’ll be more fiddly to sandwich and align
(4) it felt wasteful to piece something and shove it on the back

But your comment brought me back to reality. I don’t want to make two quilts with this fabric, I don’t have intended use/recipient, I made it because I wanted to. I don’t want to pay for twice the batting, sandwich twice, quilt twice, or bind twice! Onto the back it goes!

KalamaQuilts

as far as lining up double sided quilts, I don't know how longarmers do it, but whatever I quilt
(This assumes your quilts are squared and flat....)

find center of each side on both tops and tie on a long piece of thread. I use thick crochet thread.
Long so you can see them once the batting is on
I spray baste the bottom one, center the batting (I tape my tops to the floor but there are lots of ways to do it)
then with the top folded in quarters I eyeball align the strings for that area, then unfold and super align the strings.
then I fold back 1/2 lightly spray baste, align and smooth that half. Then same on the other side.
Takes longer to type it than do it... sounds fussy but it isn't.

pamelor

I've done pieced quilt backs too, for all the reasons Kalama mentioned. Plus another, for me the piecing is more enjoyable than the quilting so why not make something fun for the back? also, I don't really need double the amount of quilts in my house. And if it's decorative, like a wall hanging, I can flip sides when one sides gets boring. I make the back side more of a free design so it's not important whether it exactly lines up with specified borders. Otherwise trying to line it up when quilting would be a huge headache. By the time I'm done, sometimes I like the back as much or more than the front.

Karamarie

I do quilt less these days but if I start a quilt, I do finish it before any other project I may want to do. I also apply that to buying clothes - if I buy a new top, etc. I have to get rid of 2 old tops. At my age I don't need a big closet filled to the brim. It was different when I worked in an office setting, but now not so much. So I guess I apply that way of thinking when I make a quilt. Just me.