Oh wow... absolutely gorgeous. I love doing sharpie tattoos, but I've never done one of that much detail and so large. Did the ink cover alright? Sometimes mine run dry from going on skin and then it gets all bleh.
They are quite fragile. They smear if you rub it too hard, if you don't touch it probably it'll last one day looking decent before it fades. And it depends on where you put it, back or face it'll fade very, very rapidly because there is much body grease on those parts.
And I really don't know of any way possible to make it stay on longer.