It has been two years and two VERY Hard Winters and my ottoman is still going strong!! And I must admit that I barely water or take care of it, it is "hovering" above the ground on casters so it is not protected in the ground. Here is a post from 2008 when I first planted it...
The PURE Gardener, Inc.: My New Ottoman
It is dormant now but I just peeked at it yesterday -during the snow- and I can tell that it will be coming out of hibernation as soon as it warms up. Watch for new photos soon!