how much time? as long as it takes. If you buy the DJ eq thingie my two sides of jane is on it (both sides) plus journal and 'toid tins.
I saw the book and bought it thinking it looked like plenty of opportunities to practice applique.
And I did applique many blocks that could have just as easily been pieced.
There is no fabric that doesn't look good on a Jane. I used stash only, with 6 different fabrics
I pieced mine in 3 months but was on fire about the project, took about 5 years to quilt it.
I ca't begin to imagine doing it BOM because of the cost, and because it would would have twin sisters.
if you do it though you will find yourself a far better patchworker at the end. There is all kinds of fudge room in a 12 inch block with 10 or 15 pieces, almost none in a 4.5" finished block with 10-50 pieces in it
Make a few blocks using stash before you commit to it.