There are plenty of modern quilters doing this, have a look around Instagram. #bigstitchquilting would be a good place to start. It looks lovely. They do the machine quilting first, I believe. (I don't know how to machine sew, otherwise I'd have tried this.)
It generally takes me a few weeks to hand quilt a sofa quilt (around 5' × 6'), but I'm severely disabled and can only quilt for an hour or two a day. I typically space my quilting lines 1.5" apart, but it can get a bit closer, depending on the patterns I'm quilting. I suspect it's a lot quicker than many machine quilters realise. Make sure you pick a batting known to be good for hand quilting, though.