It all depends on where you put it! If you plan on hanging it on your door, it likely will only last the season. But, if you store it indoors, out of direct sun, and out of reach of children, cats, etc, it'll last for years!

Keep it out of the elements (wind, rain, sun, snow) as much as possible. Every few months, give it a spray with unscented hairspray to keep it from shedding. Over time, the flowers will become more brittle and lose colour, but there's beauty in that too!