Quilt repair advice
 

I have an old quilt that dates anywhere from 1940-1970, well love. It is an apple core design and has entire apple cores that have eroded away on top and some where the backing is missing. At first I was going to deconstruct the quilt and add new apple cores where they are missing and re-sandwich and re-quilt. This quilt only have sentimental value. It was made by my grandmother and great-grandmother (who passed before I was born). My issue is it is hand quilted. If I deconstruct the quilt I lose all the hand stitches that two great ladies placed in the quilt. Is it better to just applique pieces over the top and save the stitching? Or is it better to rebuild it completely so that it easily lasts another generation?

Id go for the appliqué.

Sounds like you want to save their stitches, which is what I'd want to do. I'd add applique if it were mine. That way you repair it, but you are adding your stitches instead of subtracting theirs. So the future generation will have even more "hands" visible in the heirloom.

Another vote for applique. Otherwise you may ruin the lovely hand quilting.

Applique!! The sentimentality is in the stitches...

My vote is for applique. I like Zozee's comments about adding not subtracting!

i would leave it alone - it has given long service - perhaps display it on a quilt rack -

I have repaired quilts like this, applique-ing pieces over the top and then hand quilting them but NOT through all 3 layers. There will already be quilting showing on the back, just add a line so it matches on the front.