Springs basically don't wear out unless they're junky. And for $250 those won't be. if that thing fails it will be fatigue. The pivots might wear out but since it's all under compression you'd have a hard time telling. Also, the page says they've been around since 2011 so the answer is probably "at least 5 years"

I'm not sure why it's better than a springer saddle and/or a cheap straight suspension post of the $15-30 variety found on inexpensive comfort bikes.