A mystery Coverlet (quilt)... Fustian but....

This coverlet is antique but what age....
I think the base fabric is fustian as there is a blue line woven in the selvedge which dates it to my limited knowledge to the latter part of the 18th century. BUT this could well have been someone making use of an old sheet when it was made. Anyone who has had linen sheets know they are probably good to use for a 100years but this fustian was made with a cotton weft and a linen warp. So I am guessing this would halve it's lifespan as a sheet.  This is all supposition on my part so if any of you dear textile historian readers call shed any light, it would be much appreciated.

This little bird delights me, it and the little dragonfly above it are the only 'random' appliques on the coverlet. And the darning in this photo is so badly done I can only think it was done in the latter half of the 20th century when people stopped darning their socks......
Click on any of the pictures to enlarge them and see the detail. All the applique fabrics seem to be a heavyish weight cotton with the exception of one fine cotton pink which has degraded in one or two places where it has been used.