Does this flower NEVER die?

When frost was first threatened, I ran out and cut a flower and three leaves from my calla 'Edge of Night' (A lovely plant... black flowers, dark green leaves flecked with silver and edged with red). The flower had opened several weeks back, so I didn't expect it to last too long in the vase.
In a week it looked like this:

Since when do flowers last longer than leaves? The frost had spared the front garden, so I went out and got replacement leaves -- which also yellowed in a week, with the flower still going strong!

At this point, a freeze had eliminated all calla foliage (along with most everything else), so last weekend I searched for a replacement to set off the lovely flower.

They are the (incredibly spiney!) leaves of my scotch thistle. Looks pretty fantastic, doesn't it? Three weeks in the vase, and still, this flower shows no signs of fading. Maybe someone slipped me a plastic one?