Meet the empty nesters who have visited all 63 US national parks - after realising 'life is too short'.<br /><br />Matt, 63, and Karen Smith, 64, became empty nesters 16 years ago when their youngest son, now 35, moved out.<br /><br />After losing friends and family of a similar age - the couple realise that life is too short.<br /><br />They set themselves the challenge of visiting every US national park and spent two years seeing them all.<br /><br />The couple have sailed down the Grand Canyon, seen wild bison at Yellowstone National Park and breath-taking views at Canyonlands National Park.
